Anxious Crows in Space

A Fermi Paradox Rambling Grounded in Evolution and Game Theory

I'm here to sell you a boring universe. Not empty --- boring. Full of things that look like us, think like us, worry like us, and then either kill themselves or sit quietly until their sun goes red.

The silence isn't because intelligence is rare. It's because intelligence, at the level we'd notice, is either dead or hiding.

WHAT GOOD'S A HALF A WING?

There's this old argument about evolution. "What good is half a wing?" The creationists loved it. If a wing needs to be fully formed to work, they'd say, how could it evolve gradually?

The answer, of course, is that half a wing is useful. It helps you glide. It helps you insulate. It helps you show off to potential mates. Evolution doesn't need the finished product to start benefiting from the parts.

Evolution doesn't build for the future. It builds for right now. A trait sticks around if it doesn't kill you before you fuck, simple as that.

Consider the human spine. Degrades after thirty. For any species, a failing spine is bad. But humans reproduce way before thirty (or used to, at least). The genes that turn your back into a problem by fifty? They sail through the filter. Evolution never sees them.

Same with intelligence.

Crows are smart. Most birds aren't. Does every bird need crow-smarts to survive? No. The crow's intelligence helps it solve problems, but its absence doesn't doom a sparrow. Intelligence, once it appears, persists not because it's essential --- but because it's not harmful enough to breed out.

Human-level intelligence is just this, amplified.

For most of our history, being clever helped us find food, navigate drama, pass on genes. It didn't threaten us because we lacked the tech to make that threat real. The downside? Nukes, climate collapse, AI we can't control. All arrives after we've reproduced. Evolution doesn't see it. Can't select against it.

Intelligence is an evolutionary free rider. It hitches along because its extinction-level consequences manifest too late to matter at the genetic level.

THE USELESS-USEFUL TRANSITION

Here's the thing nobody tells you about intelligence: for most of its existence, it's locally useful and cosmically irrelevant.

It helps you find food. It doesn't help you survive an asteroid.

A species with human-level intelligence in 10,000 BCE was just as vulnerable to a rogue comet as a species of dolphins. All that brainpower, and you're still dead if the sky falls.

The transition to cosmically useful intelligence, the kind that can deflect asteroids, leave the planet, engineer stars. It requires crossing a threshold. You need physics. You need industry at scale. You need global coordination.

But here's the trap: you cross that threshold long before you're ready for it.

The same knowledge that builds telescopes builds bombs. The same industry that could one day construct space habitats currently pumps CO₂ into your atmosphere. The same connectivity that might eventually unite your species currently spreads conflict like a virus.

Intelligence, at this stage, is giving a teenager the keys to a nuclear submarine. The capability arrives before the wisdom. And because evolution never selected for wisdom at this scale --- why would it? --- there's no guarantee the wisdom ever arrives.

Do dolphins need anxiety? No. They're fine. They're swimming, eating, fucking. They don't lie awake wondering if the other pod is building a bomb. They're fine.

We're not fine. And we can't go back.

THE GAME WILL FIND A WAY

You want to know why cooperation fails at scale? Game theory. Full stop.

Every actor has an incentive to cooperate for the common good. Every actor has a stronger incentive to defect while others cooperate. If everyone cooperates, everyone wins moderately. If everyone defects, everyone loses. But if you defect while others cooperate? You win big. At least in the short term.

This isn't a failure of morality. It's a failure of incentive structures.

Small bands can enforce cooperation. I know you; you know me; cheating has immediate social consequences. But at the scale of nations, of billions of people, anonymous, disconnected, the enforcement breaks down. There's no global police. No world government. No way to ensure the other player won't cheat first.

The result is a stable trap, a technological species that knows it's heading toward disaster but cannot coordinate to prevent it.

Nuclear weapons are the perfect example.

Globally optimal: zero nukes.

Nationally optimal: only I have nukes :)

Second-best: Fallout games (big iron on his hiiiiiiiiip...).

Worst: only my enemy has nukes :(

Terrible: İ̴͈͗s̷͙̝͋ŗ̴̞̿à̴͔͙̍e̴͈͎̅͗l̵̞̑ ̵̰͇̉̎h̸̞͋͊á̸̹s̴̬͙̀ ̴̛̝͝ţ̸̛ḥ̸̲̏͝e̷̻̱͝m̷̭͉̐.̴̼͛͜

Given these payoffs, rational actors pursue the nationally optimal outcome. Every time. Cooperation fails not because anyone is irrational, but because the math makes defection the locally rational choice.

You think aliens are above this? They do physics. They'll find fission. They'll face the same dilemma. The math doesn't care about biology.

The first man to fence common land wasn't evil. He was just playing the game as structured. Once enclosure is possible, the rational move is to enclose before others do. Same with weapons. Same with power. Same with information.

The game will find a way. It always does.

THREE WAYS THIS ENDS

Given the trap, what happens to a typical technological species?

1. Rapid annihilation.

Some species don't survive. They trigger their own extinction within centuries of reaching the threshold. In geological time, they appear and vanish in an instant. They leave no traces we could detect from afar, just a brief pulse of industrial chemicals in an atmosphere, maybe, before silence.

2. Long-term struggle.

Some avoid annihilation but never solve coordination. They muddle through, century after century, always on the edge. They might develop partial solutions (arms control, international institutions, cultural norms) but never full cooperation. They remain planet-bound, resource-constrained, largely invisible. They aren't building Dyson spheres or broadcasting existence. They're just... surviving. The galaxy could be full of such worlds and we'd never know.

3. Rare transcendence.

A tiny fraction solve the trap. They develop global cooperation, escape the prisoner's dilemma, expand into their solar system and beyond. These are the civilizations that might build megastructures, launch generation ships, transform into post-biological entities. They are also, by definition, rare—otherwise the galaxy would be noisy with their activity.

Note what this means: the species we might hope to detect, Kardashev II and III, are the exceptions, not the rule. Most intelligence never gets there. Most either dies young or lives quietly, never leaving a detectable mark.

bonus point.

T̸h̶e̷ ̸v̸̞̤̿̈ö̸̡̰́͂ị̵͔̐d̵̰̠͓̘̦͒c̵̖̪̚͝ơ̸̳̬͂n̵͈̕͠ś̷̹u̵̲̓m̷̹͍͝ẹ̸̕͝s̴͓͐̽ ̷̖̽ù̵̺̚s̵͎̐̓ ̷͍̜̀͌a̶͙̐͂l̸̼͓̈́l̶̪̍͑.̷̨̞̐͝

WHAT THIS MODEL (?) DOESN'T CLAIM

Let's be clear about boundaries.

I'm not claiming artificial intelligences don't exist. They might. They're black boxes with inscrutable goals. Could be out there, silent for reasons we can't fathom. But we don't need them to explain Fermi, so invoking them is unnecessary.

I'm not claiming transcendence is impossible. Just rare. The species that solve the trap are the exceptions, and their rarity explains why we don't see obvious signs.

I'm not claiming intelligence is useless. It's locally useful, which is why it persists. It's just not protective at the species level until very late.

And I'm not quantifying anything. I don't know what percentage survive, what fraction become strugglers versus annihilators, how many transcend. The model identifies a filter. It doesn't measure its mesh size.

THE CROWS IN THE DARK

So where is everybody? --- asked everyone, everywhere, eversince.

T̶h̸e̶y̵ ̷a̷r̴e̵ ̴i̷n̵ ̶y̵o̵u̵r̴ ̸w̵a̷l̸l̷s̶. Sitting on their worlds, moderately intelligent, moderately anxious, moderately doomed. Some will kill themselves. Most will struggle indefinitely. A tiny few will figure it out and leave --- but they'll leave quietly, because the universe punishes loudmouths.

The silence from the stars doesn't mean intelligence is rare. It means intelligence, at the level we might hope to detect, is either short-lived or quiet. The universe could be teeming with species much like us, clever enough to worry, not clever enough to escape. Each listening to the silence and drawing the wrong conclusion.

We're not alone. We're just not loud. And neither, probably, are they.

The crows are out there, sitting in their own dark forests, cawing into the void and hearing nothing back. Not because no one's there. Because everyone's too busy surviving to shout.

Bye!

- M.O. Valent, 07/03/2026

Better than RKVs?

DESTROY ALL CREATURES, THEY CAN’T BE REGENERATED.

“Destroy all creatures. They can’t be regenerated.” is in the text box of two of the most iconic cards in the card game of Magic. Wrath of God, and Damnation. Simple, rigid, brutal — even to those not at all familiar with the game. They spell and evoke a sacred cleansing, or an unholy doom.

And it gets even better, or worse (depending on your worldview), when combined with the aesthetics of the illustration by Kev Walker in the set Seventh Edition (2001) and later in Planar Chaos (2007).

 

SALVATION THROUGH ANNIHILATION

“Destroy all creatures. They can’t be regenerated.” — The first and only words they heard from their creators before being launched in the face of the abyss.

In Fred Saberhagen’s "Berserker" series (1967), ancient machines created to fight a war that no longer exists go rogue, resulting in the attempted erasure of all sentient life in the galaxy.

The concept was later expanded into the Berserker probe or civilization:

• Potentially a type of Von Neumann probe, self-replicating and rapid-spreading.
• Rogue AI or an intentionally built exterminator.
• Working under the directives of a dead creator.
• Its goal: terminate all intelligent life before it becomes a threat.

Such an invention proposes a possible solution to the Fermi Paradox.

• Life is common, but intelligent life is rare, because it is being systematically wiped as soon as it makes its presence known.
• The galaxy is then full of dead, silent worlds.
• Civilizations that know of such probes or civilizations choose to remain silent.

The silence comes from a deep desire for survival, both from those alive today and those who are long gone but left the Berserkers behind.

Potentially, every civilization understands the rationale of becoming a Berserker themselves and adopts it.

Which leads us to the Dark Forest hypothesis.

The universe is like a "dark forest" where every civilization is a hunter. Since no one can know the intentions of others, everyone stays silent — or shoots first.

Popularized in Liu Cixin’s novel The Dark Forest (2008), the second book in the Remembrance of Earth’s Past trilogy (The Three-Body Problem series).

Key Logic:

1. All civilizations want to survive.
2. Resources are finite.
3. You can never truly know if another civilization is friendly.
4. Therefore, the safest move is to stay hidden or eliminate others preemptively.

This results in:

• A "cosmic silence" — nobody is broadcasting, because to do so is to risk death.
• A universe full of civilizations, each afraid, each hiding.
• When someone does speak, others might interpret it as a threat and destroy them — not out of malice, but rational survival.

THERE IS NO STEALTH IN SPACE

In principle, there is no way to hide oneself from external peering across the vastness of space. Sufficiently advanced telescopes and sensor arrays can and will detect radio emissions, leakages, biosignatures, and technosignatures from potentially thousands of light-years away. We are, year after year, inching closer to that potential.

Plus, the Earth itself, as old as it is, has been emitting bio-signatures for as long as 3 billion years, and as far as we can tell, we haven’t been visited or exterminated yet. Worse still, we have been broadcasting into space for about 100 years — had anyone been listening to it nearby, say within 50-ish light-years, we would have received a response, or known about them by now, right? This uncertainty only further stokes the apparent silence in the heavens.

As far as we can tell, there are no technological indicators nearby, at least not ones that point to a far far more advanced civilization than ours. Such as Dyson Swarms.

But I dare to propose that no one builds Dyson swarms in the way we expect. If a civilization factors existential risk into its engineering decisions, then a Dyson swarm becomes nothing more than an expensive lighthouse, and a potentially deadly one at that.

Sure, absorbing even just 1% of the Sun’s total energy output would mean nearly limitless energy for humanity, but it would also signal to the entire Orion Arm that we are here. Anyone observing the stars for a sufficiently long amount of time would notice that now our Sun suddenly dims in regular intervals compatible to that of a techno-signature, and upon realizing that, we just gave them to chance to respond accordingly.

If there's one thing Magic, game theory, and war have taught me, it's this: giving your opponents a choice is almost always a mistake.

We then revert to low-yield Dyson swarms at (<1%), because the energy need still exists, but over-doing ourselves above a certain signal-to-noise threshold is dangerous.

In the dark forest, the most negative outcome is annihilation, and the least negative is staying silent. The neutral option however, given you have the opportunity to make the first move, is to strike first before they become capable of doing so to you.

THERE ARE NO SECOND CHANCES IN SPACE

You are a multiplanetary Kardashev 0.8 civilization, and you have found 10 potentially habitable planets within 100 light-years from your star. Great job! Can we jump to interstellar colonization? Not yet.

We need to study those worlds, and see if they actually harbor any kind of life, and if that life poses a threat to our own existence.

After almost a century sifting through space and watching those systems closely, we have determined:

7 of those worlds are far too primitive or sterile to represent danger. Prime candidates for safe exploration.

• Planet A 25ly away from ours has weak bio and techno-signatures of a 19th century industrial society. K 0.5
• Planet B 50ly away from ours has strong bio and techno-signatures. It's not clear how much advanced they are, they could between a century or a few decades behind us. K 0.75
• Planet C 100ly away is clearly on the same level if not more advanced than us. K +0.8

Threat Assessment:

• Civilization A - Low priority, they don't know we know about them. Can't do anything about us for a good while, but they are close enough that once they do - they will have the upper hand.
• Civilization B - Alert, they might know about us, or be very close to finding out we exist. We are lucky to have found them first.
• Civilization C - HIGH ALERT, they probably have known about us for a century or more. If they attacked us immediately upon discovery, then we have to retaliate and scatter before we are wiped out soon. If they didn't attack us, then we have the advantage of attacking first.

There are a couple creative ways we can deal with those. The safest option however, with this little information, great technological and time dilation gaps, in all three scenarios, is to attack first.

However, our mere existence here indicates there is something else at play.

Civilization B likely knows about A. And C knows of both us, A and B. Yet they have done nothing, apparently. Civilization C is also alive as far as we know it, so that's weird.

Let's wait to see what happens to the others while we arm ourselves for a potential conflict.

The swiftest way to eliminate a planetbound civilization, like ourselves, would be to deliver them a Relativistic Kill Vehicle - RKV to their homeworld.

A single 100 kilogram steel sphere traveling at 99.99% the speed of light would carry enough energy to deliver about 150 Gigatons of TNT, equivalent to a 2km-wide asteroid impact at 17km/s. Scale that to about 50 tons of steel, and we got ourselves 75 Teratons of TNT, or equivalent to the dinosaur-killer asteroid in our hands. If we want to maintain the impact but reduce the projectile size, we have to make it even faster, at near-near lightspeed.

That should be it, right? Sit a container-sized projectile atop a really large proton or matter-antimatter rocket, position a few whipple shields to protect the payload and rocket from interstellar debris and voilà, shoot and forget.

Congratulations, you have just missed your target, and now they know you exist!

A planet is a big target. A container-sized projectile traveling at 99.99% lightspeed should hit it — but only if you can predict its position 25 years in advance, down to the hour. That’s a hard ask.

That requires precise and near-perfect information to achieve, or insane navigational input on the warhead. Workable, but still impractical.

There is also the issue of false hits. The projectile hits a moon, or large enough asteroid in their target system that the whipple shield is not able to protect it, the thing explodes in interplanetary space without causing the intended damage. That also includes unaccounted rogue planets in interstellar space.

Alright — just send more!

You can fire a thousand RKVs to ensure one or multiple hits on a planetbound target without any defenses. That would work. But your fire cone would still have to be very tight. And if you fail to exterminate them, they will know exactly where in the sky to look for you. That could work for Civilization A — just double-tap them. Better safe than sorry.

WHEN PLANETARY XENOCIDE ISN'T ENOUGH

Getting rid of an equivalent Type 0.8 civilization requires a little more work than that. Like us, they may have expanded across their system, making single-target annihilation ineffective, we don't know for sure how many targets we would need to take down in their home system.

You count at least 5 Earth-sized planets in the system, with possibly 50 minor bodies such as moons and asteroids, with about 10,000 major space habitats and stations. That's 5 high value targets with 10k moderate ones. Let's say 10,100 hits is an acceptable mission result. Instead of a couple hundred to a thousand, we now need over 10,000 weapons with 100% accuracy to get the job done.

If for the previous one we needed about 1,000 RKVs to ensure 1-2 hits. For this one, given a similar statistical success rate, we need to deploy roughly on the scale of 5-10 million weapons.

This suddenly sounds like a bad plan now, that's 325 million tons of steel just for the payload, not to speak of the amount of antimatter needed to power it, and the firing flash we will send into space. And firing slowly one by one would give our target enough time to react in the case we don't get them in the first shot. At 50ly distance, that also means they will know they have been attacked 1.8 days in advance, giving them time to counterattack if they have similar weapons, or even, counter our attack before retaliating. Too risky, too flashy.

It gets even worse if we wanna attack Civilization C the same way. Imagine hundreds of thousands of habitats, or even aiming at neighboring star systems to theirs as well if they have gone interstellar already. Their response window to our attack is even wider at 3.6 days, and it would only be worse would they be at 1000 light-years from us, with a month to respond (because light still travels faster than our projectiles).

In conclusion, RKVs aren't the perfect weapon for interstellar warfare. They are effective however, if:

1. Target is relatively close. Within a few dozen light-years.
2. Target is planetbound. Lower technological tier.
3. Your weapon travels at near-C. RKVs of lower velocity can still be efficient in interplanetary conflict.

Failure to obliterate your target in the first hit with the least amount of weapons results in your own likely annihilation, either by their counterstrike or by a preemptive alliance of eavesdropping civilizations. Undesirable, unless you point your weapons in every conceivable direction at once. Spray and pray, it's the Berserker way.

EXILE ALL ARTIFACTS, CREATURES, ENCHANTMENTS, AND GRAVEYARDS

Is the text of a desperate Farewell being played for all its modes.

Meet the MIRP - Matter-Antimatter Induced Radiation Pulse. The perfect Berserker Probe.

If matter-antimatter reactions can be tamed, then sending a few probes behind our grapeshot would ensure another round of sterilization. Not only to propel our masses, but to flashbang their home system with radiation. Intentionally detonating an M-AM core would release intense amounts of radiation, thousands of times above their background levels and likely way above what usual radiation armor in space stations can deal with.

Since M-AM annihilation reacts one-to-one to release pure energy, we could perhaps, react a few billion tons of each, creating an artificial supernova at roughly point-blank. Total annihilation by gamma ray burst without the hassle of building 1 billion steel spheres and yeeting them at near light-speed. It could even easily pass off as an interstellar rogue asteroid. And the flash? Easily dismissed as distant supernova, or even drowned in background noise since it is so localized in effect.

And we know how dangerous that can be, take the Late Devonian mass extinction event, about 360-375 million years ago. Where supernova radiation is theorized to have contributed to mass extinction through ozone depletion and increased UV exposure, due the presence of iron-60 in the rock layers. The estimated energy flux is on the order of 100 kJ/m², mostly because of atmospheric attenuation — so while it would be effective against space infrastructure, it would have to hit way harder than that to pose an existential threat to life on the surface of an Earth-like planet if we wanted to fry all Life.

Which makes me wonder. Has Earth been attacked before? Have we outlived our aggressors perhaps? I hope so. Would the solar system have been someone else's colony, that got targeted, it is perhaps not so far off. (No I'm not entertaining the Silurian hypothesis.)

Would a 1000 solar-luminosity flash occur over a split second at under 1 AU from Earth, it would release an energy dose of approximately 13.5 GJ/m² — over 13,000 times more intense than the Late Devonian extinction event. And it would remain lethally effective out to 10 AU, covering all, if not most, of a civilization’s core space infrastructure and habitats.

The real challenge lies in gathering the 2.2 trillion kilograms of antimatter to complement an equal mass of conventional matter. But how much is truly required depends on proximity to the target — or, alternately, on deploying many smaller units across key orbital lanes and gravity wells.

Gathering this much antimatter is a non-trivial issue, but one already accounted for if one does intend to fire RKVs at near lightspeed anyway. I'm just proposing a far more efficient use per kilogram, at a near 100% kill-rate.

Aside from that, it has nearly infinite range, nearly infinite efficiency and nearly infinite accuracy, it is also fragile, so tampering with it if found could possibly trigger a premature detonation. Differently from RKVs which only work effectively at a limited range due informational gaps, such a gamma-ray burst bomb wouldn’t give away your location in the slightest, because it's an area effect, it could have been the system next to the target, or someone in the far edge of the galactic arm.

It could have been wandering space as a sleeper agent, and detonating upon sensing radio waves at sufficiently close range.

It could possibly be maneuvered out of the system to mitigate its effect if they realize it can’t be disarmed, but that assumes the target fully understands what it is dealing with in time to act upon it. And that’s unlikely, resulting or requiring an ungodly amount of paranoia.

And that fulfills the requirements for the dark forest scenario to be sustained.

• Civilizations value survival above extinction.
• Civilizations can attack with 100% accuracy and 100% efficiency at extremely long distances.
• Civilizations can attack so with near 100% anonymity, as to not invite a counterattack.

It makes the forest completely mined and booby trapped, or in the process of becoming so.

Plausible by engineering, invisible by design.

Goodnight.

- M.O. Valent, 10/06/2025

SHORT STORY | DAY OF RECLAMATION

I woke up that day with my mom shaking me off my bed.

It was early in the morning - and she was extremely nervous.

Where is dad ? - I asked

All she could say is that we were going to meet up with him later

I had to go with her

I didn't have time to take any clothes of my stuffies... She shoved me in the car and took off like crazy

The road were packed with people doing the same, some didn't managed to pass through the traffic jam and ran with their kids - mom was ruthless and bumped everything off our way

I was tired and scared, before I fainted, i looked up the back window and saw what i could only describe as hell.

I woke up by noon, at some sort of shelter - mom was no more, and they said i was a brave survivor, well, they were too... The military always full of brave men and women, the best of the best of our people - despite the positivity in their words, their faces showed they had already accepted defeat...

Not even before the end of the day they turned their radios off - the screams and distress calls were too much...

By the next morning, we all had to leave because they had found us, but for the rest of the day - it was eerily calm as we traveled in trucks to a countryside bunker with better security and more food...

We were being invaded, by who - i would found out a couple of weeks later.

When I was testimony of the most beautiful and terrorising scene to this day... They outnumbered even the darkest swarm of locusts, but in opposition to that, they had the grace of a dancer, always knowing where to hit, where to move

Always moving forward

Never stopping to celebrate

Or mourning their dead

They did take little of any damage or casualties in that macabre ballet

Despite our best efforts in the battlefield

We moved to the countryside, where we once heard there was no incidents over there... Which held true for a year... The surprise massacres became more of a routine

We could barely stay on the same place for over a month, we were reduced to scavengers and gatherers - and as they pierced further into the land, we attested to their true nature...

Their mere sighting was enough - not to cast fear or terror but to summon Chaos itself.

The generations after me canonized them as unrelenting forces of nature, as if it was natural...

They had little to no respect for any living being, that flew, crawled, or swam... Little did matter to us what they wanted, dialog was futile in this new world that had taken over our holy land, be it with the invaders or our own kind, now divided...

Now, thirty years later, the most powerful of our survivor groups have gathered together, and today is the day of reclamation, the day we will avenge our fallen parents, brothers, and children, and purge for once - these Humans off what once was our beautiful home!

SO, I BREWED A WHOLE MTG SET | ZENDIKAR BESIEGED BLOCK | Part 1

A SEGWAY INTO MAGIC, RATHER THAN SCIENCE-FICTION

As of mid-2023, Zendikar has once again been invaded, this time by the machines and Elesh Norn in March of the Machines. Though I ain't as excited about any of the new sets since Kaldheim, yk because I have barely any money for selected cards, and none for boosters and expansions. But it was cool see one of my favorite planes featured in one of the cards of MOM.

When I was introduced to Magic: the Gathering in early 2019, we had just left War of the Spark and Guilds of Ravnica, so I have quite an emotional affinity with the plane of Ravnica, getting and playing with a simple Golgari zombies standard deck for a while because it was the colors my dad used to play with in the 90s and early 2000s. But I have since moved on from Golgari and into Gruul, that's when I started playing Commander circa 2021, with now a landfall deck, I figured over time that the plane of Zendikar and its expansions had many interesting things to offer, from my own landfall needs and plenty of Eldrazi for my cousin. I have now as of 2023 moved away from landfall (I still have that deck), venturing into the Jund shards with a bit of a cheap but scary commander, but nevertheless, the planes of Dominaria, Ravnica, and Zendikar have so far been my favorites, both for cards and land arts.

During that period of development, I tried joining some magic communities, making and losing friends along the way, and learning more about the game and its history. Though I must admit, I never read any of the books or comics about the original planes of the MTG multiverse, so here is where my experience diverges from some of you.

What I know from the lore of magic, comes in the form of a few promotional pamphlets, mtg story cards, their flavors, and of course the wiki. And it does surprise me that apparently, the original invasion of Zendikar by the Eldrazi has been left, nebulous and mysterious (I bet that is kind of the point), an ancient menace once imprisoned in the hedrons, now set free to consume the whole plane. Well, I'm now part of the Staff over that discord server, and I brew cards for fun as we usually do... Why not tackle that, with my own janky set with janky lore?

If you like what you're about to see, I invite you to our server, where we will be hosting a Modern game session with cards from this set over the weekend, days 2, 3, and 4 of June.

"May The Storm Begin!"

So we open Zendikar Besieged with the words of command of Iryzek, World Breaker. It brings the resurgence of mechanics like Landfall, Trap, and Intimidate, and the creature type Ally, borrowing many card effects, keywords, and strategies from the sets 'Battle for Zendikar', 'Zendikar Rising' and 'Rise of the Eldrazi'. But the heart of Zendikar Besieged lies in two aspects, Tribal Eldrazi spells, and the new mechanic Rift.

Rift (For each generic mana in this spell’s total cost, you may tap an untapped Eldrazi you control rather than pay that mana.)

So rift does drink in the same pool as Convoke and Improvise, it could be summed up as an Eldrazi convoke, big creatures and spells cheated for little to no mana for as long as you have many Eldrazi Scions.

We've decided to give it ward 2, for story flavor

Spells with rift are often colorless, although black, green or blue with devoid are also present, never appearing in red or white. There are quite a few multicolored cards in this set, and some cards even care if you rifted a spell to trigger abilities. The overall theme of Zendikar Besieged is to explore the precise time period when the Eldrazi first invaded Zendikar, as in previous real Zendikar expansions this is told as having happened in the deep past already. A time long before the hedrons were made and the Oath of the Gatewatch was formed. Engaging with the desperate struggle by the side of new ancient planeswalkers against the relentless onslaught of the Eldrazi titans as they threaten to consume the very fabric of the plane.

a demonstration of what creatures with rift are like

To better explore the rift mechanic and the storyline, the set includes new 162 cards (might sound small, but 150-ish per 300 cards in a set are reprints), with many Eldrazi creatures for the colors that have rift, while red and white focuses on countering the Eldrazi and creating either a strong defensive line or advancing against Eldrazi players, while also including some notable cards from my usual janky-ass brewing.

I have two planned expansions, which will receive the attention on cycles and set-building and balancing that the main one didn't get. After playtesting, I will post a follow-up post with highlights to broken, overplayed or underplayed cards from this set.

LAND CYCLES

SANCTUMS & NEXUS

Sanctums were sacred places either under siege or already corrupted by the shimmers of the Eldrazi invasion, its mana being partially shifted into colorless. In-game, they enter tapped and offer colored or colorless mana, however, each sanctum provides a color-flavored effect for (4). Each color but blue and colorless has a sanctum, having eldrazi nexuses instead, and black and green are eldrazi allies.

SKYCLAVE CYCLE

Zendikar's roils are very unstable, the constant and regular shifts in the landscape make it near impossible to build permanent settlements on the surface, societies however found out that buildin up floating islands (or mountains) were the better alternative, thus were born the Skyclaves. To represent Zendikar's resistance against the Eldrazi invasion and the fortress status of the Skyclaves, these fast lands enter the battlefield tapped unless you sacrifice a colorless non-land permanent, preferably an eldrazi or artifact, as if you were fighting them off your field. Perhaps a little too oppressive for players who do not play a lot of colorless permanents in their deck or do not make them, maybe a little more viable in commander.

RUINS CYCLE

There are mentions to ancient ruins present across Zendikar as of 'Rise of the Eldrazi', ruins many wrongly believe were built by them. But since we are at the time of the first invasion, let's tackle the ruins! As the carnage against the Eldrazi rages on, many roils and places were brought down to crumbles, but that doesn't have to be a bad thing at all. In Zendikar Besieged, you can call for a Ruin and its features at the cost of no-land ramp for that turn.

MISC UTILITY LANDS

Zendikar Besieged also includes some mixed utility lands for colors other than blue and green.

NAMESAKE OF THE SET

I feel this set wouldn't be complete without a namesake card, and what better for a Land-focused plane than a namesake legendary land? For non-eldrazi combat it just buffs your basic lands (or better yet, roils), and it offers intense combat interactions against Eldrazi.

OTHER LEGENDARIES

Unfortunately, ZBS lacks a lot of legendary creatures or planeswalkers, as many figures that appear in the future Zendikar blocks weren't around or born yet. Instead I have brought six new legendaries, two creatures (Iryzek and Erevan) and four planeswalkers.

STORYLINE

In the last few years, several mana sources across the roils of Zendikar have been depleted of their energy by a mysterious shimmer. Over the course of months, the shimmers expanded draining the mana and life energy of creatures and landscapes alike, until finally bursting open with interplanar rifts, the Eldrazi have chosen Zendikar as their prime target. At first, the rifts brought small crawling and flying eldritch beasts, which devoured and conquered vast territories around the shimmer, when they started attacking the aerial Skyclaves was when the Eldrazi became not only a problem of the druids and vampires down on the surface. When the Eldrazi drones started bringing the shimmers to the Dimir Skyclave, bringing it down with the rifting of a giant Eldrazi, the Makindi Empire realized the true threat of the extraplanar invaders, but it would seem too late for an effective reaction.

After the Dimir Skyclave fell, and its mana source devoured, the eldrazi drones and scions all across Zendikar started creating more focal points of the shimmer, from where larger rifts would form, allowing flying skimmers and larger more deadly eldritch monstrosities to enter the plane, coming from the Blind Eternities.

EREVAN'S JOURNEY

Over the course of the Great Rift Storm, one notable wizard, Erevan Reth traveled non-stop across the plane to study the shimmers and find a way to use them against the Eldrazi, helping whoever stood in his way and did not have any tendrils. He stood upon the precipice of Akoum, his eyes fixed upon the swirling maelstrom of the Blind Eternities. With an arched brow and a sinister smile, he gazed into the chaotic abyss, a realm of raw potential and untamed energy. As Erevan prepared his arcane rituals, his eyes burned with a newfound intensity. He envisioned a future where he would not only fight against the Eldrazi but dominate them, turning their own otherworldly might against them, and the tapping of the Eternities always gave him visions of immense and unspoken horrors. Yet, he was undeterred, driven by an unyielding desire to free Zendikar, his home, from the clutches of the Eldrazi.

Erevan used his mastery of magic to try and sustain the rifts Eldrazi used to invade Zendikar, using them to access other roils and warn its inhabitants of the new menace. He eventually learned to open the rifts himself to draw upon the chaotic energy, augmenting his spells and wielding the eldritch forces against the Eldrazi horde.

But Erevan was only one, trying to organize a plane-wide resistance was nearly impossible with so much to risk and so many enemy nations and clans. And with the shimmers converging back in the roil of Akoum, it became even harder to convince the people that the Eldrazi menace had not been defeated yet.

The Eldrazi united to enchant a single gargantuan shimmer, which opened the rift that brought the horror self-introduced as Iryzek, World Breaker, pronouncing his thundering command "May the Storm Begin!".

Iryzek demonstrated itself to be a formidable foe and general to all forces that charged against the Eldrazi, the gargantuan tripod seemed almost omniscient of every move against it, rifting skimmers and scions around it like flies fly around a camel. It alone devastated huge areas of the roils across Zendikar, recklessly throwing his own brood against battalions of the conclave and fleets of kor like a giant beat stick, disappearing as fast as it appeared the first time. And wherever there was enough eldrazi losing a battle, Iryzek emerged to turn the tide in their favor.

During one fateful battle against Iryzek, as the Eldrazi unleashed their unholy might upon Zendikar, Erevan's connection to the Blind Eternities surged to unprecedented heights. A surge of raw energy coursed through him, threatening to consume him, yet he embraced it, his essence merging with the boundless planeswalker spark that had lain dormant within him.

In that moment, Erevan ascended, transcending the boundaries of Zendikar. He became a planeswalker, a being capable of traversing the vast planes of existence. With newfound power coursing through his veins, he emerged from the chaos, his form radiating with arcane energy. However that surge seemed to have banned him from Zendikar forever, Iryzek had banished the only one who had learned of its plans into the uncharted realms of Alara.

Despair and desperation consumed Everan, his once keen eyes now burned by the searing glimpses into the blind eternities. Through tear-filled eyes, he watched as Iryzek, his greatest adversary, shrunk to insignificance amidst the swirling mists. But then, a revelation struck like lightning in his mind. "No! It can't be true! THEY ARE THREE MORE!" Everan's anguished cry echoed through the empty void. The realization hit him like a thunderclap—the World Breaker, Iryzek, was merely a pawn, a servant to the unfathomable power of the three Eldrazi titans.

At that moment, his despair transformed into a fervent resolve. The fate of Zendikar now intertwined with the destiny of countless worlds. Everan Reth, with renewed determination burning within him, vowed to find a way back, to rally the forces of good and defy the unthinkable might of the three Eldrazi titans.

THE ELDRAZI CONVERGENCE

Meanwhile, the Makindi Empire forces rallied under the banner of resilience and unwavering determination. Led by the skilled planeswalkers, Iwyss and Nyxara, they embarked on a perilous quest to confront and defeat Iryzek, the imposing World Breaker, who threatened to bring Zendikar to its knees. With Iwyss's ability to commune with the wild and summon mighty beasts, and Nyxara's mastery of deceit and manipulation, they formed an unlikely but formidable alliance.

The battle against Iryzek was fierce and unforgiving. Iwyss's summoned beasts tore through the Eldrazi minions, rending them limb from limb, while Nyxara employed her cunning tactics, weaving illusions and traps to ensnare the enemy. The Makindi Empire forces fought with unparalleled valor, their collective will focused on one goal — to entomb Iryzek and halt the Eldrazi invasion.

Iwyss called upon the very essence of Zendikar itself. The land responded, its ancient power surging through her, charging her final strike. Evoking the aura of a Craterhoof and with a thunderous roar, she delivered a devastating blow, causing Iryzek to stagger and finally crumble.

But even as Iryzek crumbled and the Makindi Empire forces rejoiced, a strange unease washed over them. The victory tasted bittersweet. Whispers lingered in the air, faint echoes of the Eldrazi's warnings. The shimmers of doubt and uncertainty danced at the edge of their perception. Though Iryzek had been defeated and entombed deep within the roiling depths of Zendikar, a lingering question gnawed at their souls. Something was not right. The lingering shadows of the Eldrazi's cryptic words haunted their thoughts, casting doubt on the true nature of the threat they faced.

Years stretched across Zendikar as Iwyss and Nyxara traversed its treacherous landscapes, battling relentlessly against the seemingly endless hordes of Eldrazi drones. Their efforts, valiant as they were, felt futile against the overwhelming numbers and spread of the Eldrazi corruption.

In the midst of their ongoing struggle, two formidable planeswalkers, Nahiri and Sorin Markov, arrived upon Zendikar, each with their own motivations and hidden agendas. However, as Iwyss and Nyxara shared the harrowing tale of Zendikar's plight, the urgency of the situation compelled Nahiri and Sorin to set aside their differences and join forces in an alliance.

But the immense power wielded by Nahiri and Sorin acted as a beacon, drawing the attention of all three Eldrazi titans simultaneously. The unthinkable had occurred — their combined presence had provoked the full might of the ancient horrors that sought to devour Zendikar.

With the stakes at their highest, Iwyss, Nyxara, Nahiri, and Sorin realized they needed assistance beyond their own capabilities. They turned to the elder spirit dragon, Ugin, a being of immense wisdom and understanding. Ugin's arrival heralded a glimmer of hope, as his ancient knowledge of the Eldrazi offered a new path forward.

Together, Ugin, Nahiri, and Sorin devised a daring plan to deceive the Eldrazi Titans. They harnessed the inherent nature of the blind eternities, weaving a complex illusion that would entice the Titans to fully traverse into Zendikar, where their physical forms could be fought. This convergence would be the key to their entrapment. Nahiri, the Lithomancer, crafted the Hedrons, powerful artifacts capable of trapping the Titans and their minions. As the Eldrazi titans fully manifested within Zendikar, their hunger for the plane intensified, blinding them to the trap that awaited them.

The conflict raged on, a cataclysmic clash between the combined might of Ugin, Nahiri, Sorin, and the Eldrazi titans. The land trembled, the sky cracked, and the very fabric of Zendikar strained under the weight of the battle. Yet, the planeswalkers fought on, their determination unwavering. The Eldrazi titans, lured by the bait, unknowingly walked into the waiting jaws of Nahiri's Hedrons. The very essence of the Titans was bound within the unyielding stone, their minions stripped of their purpose and left powerless.

The Eldrazi threat was far from extinguished. The Titans may have been ensnared, but the insidious tendrils of their presence remained, and the struggle to cleanse Zendikar from their influence was far from over, and eras would pass before the Eldrazi menace would be again, freed.

- M.O. Valent, 31/05/2023
- M.O. Valent, edited 02/06/2023

OTHER | SEEKING CREMATORIA-LIKE WORLDS | PART 2

PREVIOUSLY, ON HARD SCI-FI...

We want a planet that:

Is somewhat habitable, but only if lighting conditions are just right, that is - it has an overilluminated side and a dark side. In which case, life would need to move or cover itself when the surface passes through the overilluminated side, and do its thing when it is dark until day comes again. Like Crematoria from Chronicles of Riddick.

EXPLORING WAYS TO MAKE CREMATORIA REAL:

From the previous post...

• Trojan planets around single stars
• Trojan planets around binaries

 Now exploring...

• S-type planets in close binaries
• Dying binaries
• Luminous black holes

LIFE BETWEEN TWO SUNS

Since we've already discussed how binary systems work in the previous  post, let's jump straight into a sketch of my plan for this setting:

Now, although in my sketch the stars are set in a 1:1 mass ratio, that will definetly not be the case, both for being a lone binary, and because we will need a generous safe zone around our planet's orbit in order to have minimum gravitational disturbing from the other star.

Since our planet needs to be sufficiently illuminated by the other component, we can already infer it lives within a close binary, which means we will have other P-type planets in the system as well, and this world would be actually a captured planet by one of the pairs.

If we make the parent star sun-like and put the planet in the habitable zone, then we would have to put the other component at +3 AU away, which is observationally bad for us since the illumination of the secondary pair would drop down to <10% of the solar constant.

But if the parent star is small, such as a red dwarf or orange dwarf, we can put the other brighter star much closer, it also helps that we get a significantly larger planetary disk around stars with mass disparity like that. In that case we will explore two sub-scenarios, in which this mass ratio is 3:1 and 2:1, the most common mass ratios for binaries.

3:1 case, system must be smaller than 0.26x the orbital separation

A ~ 1.00 Msol, 1.00 Lsol, 1.00 Rsol, 5778 K - G2V yellow dwarf

    Mean HZ for A: 1.00 AU

B ~ 0.32 Msol, 0.03 Lsol, 0.40 Rsol, 3800 K - M0V red dwarf

    Mean HZ for B: 0.21 AU

Orbital separation set to be at least 4x that of component B's habitable zone, or about +0.80 AU.

With minimum requirements, the solid airless surface of the planet would be at 310 K or 37°C, but we can cool it down to about 20°C if the parent star orbits the brighter star at a distance of 0.93 AU. Slap it a moderately thick atmosphere at 0.5 bar for an Earth-sized planet, and we got ourselves a simmering 50°C of surface temperature, with some 70°C at the equator, for a 24 hour rotational period.

That average temperature will ocillate between 32°C and 79°C as the planet orbits and points towards or away from the brighter star, changing irradiance between 1.47x and 2.63x the solar constant. These changes occur very quickly over the course of 66 days, but the planet is tidally locked to its parent star, making it a seasonal eyeball planet.

If we want to make it so it is not tidally locked, then the we can place it a bit further away at some 0.30 AU, decreasing the average temperature from 50°C down to 33°C, with an average irradiation of 1.50x the solar constant. Ocillating instead between 4°C and 87°C.

Because our red dwarf parent is quite large, we don't have to worry about sudden violent X-ray and UV flares even though we have a thinner atmosphere than Earth does. Plus, given we know the Earth's atmosphere cools at roughly 0.5~1.0°C per hour (depends on place, at my region it is roughly 0.8°C/h), we can tune the planet's rotation period to cool down to an acceptable level before heating up during the day, so if we want the temperature to drop from some 60°C during the day, down to 20°C at night, we'd have to set night-time duration to some 50 hours, which means our planet should have a rotational period of at least 100 hours to have decent cooling.

The rotational period of 100 hours bring the equator temperature to some 50°C as well, which means that during the night we have it dropping to 10°C. But that's only on the side of the planet which faces the two stars at once, we might not even have enough exposure time to hit some 70°C for most of the year. When the planet finds itself between the two stars the brighter side heats may cool down to some 14°C on average, and the dimmer side to a freezing -60°C. Because of the planet does not stop in this position for long, these potential extremes might not be reached, instead staying between well 70°C and -60°C in the equator across the whole orbit.

But temperatures might actually be stable and comfortable towards the planets poles given the softer ever setting suns or just by being in a temperate zone, though in general the whole planet's temperature changes drastically over the year.

We should also give it vast oceans, so we have ices and decent temperature buffers, so we don't end up with a venusian planet. Now, depending of the latitude, one will still get hot deserts during the day and freezing cold nights, and one half of the planet will always be considerably colder than the half facing the brighter star. So far, it seems we've accomplished our goal with moderate success.

After days in the dark, the brighter sun finally rises, thawing glaciers and lakes to form rivers which will flow fresh for the next two days until it sets again. Clibanus' thin atmosphere allows for stars and the system's outer planets to be observed even during the day, despite the radical changes in irradiation, flooded plains allow consistent liquid water for life

Compared to the original Crematoria, unless the atmosphere can dissipate the heat twice as efficiently as the Earth does, the planet of the movie cannot have 52 hour days, not can have the extreme temperature differences we see in the movie from 370°C to -180°C.

By default, this arrangement is pretty common and actually pretty likely to occur in nature, HOWEVER one thing I've stated at the start is that given  this planet is very close to the secondary star, it is possible that it is a captured planet, thus it might also sport other quirks such as high orbital inclination, high eccentricity, retrograde motion as well. The high eccentricity in particular seems like an interesting way to vary the temperature extremes even more, as well as varying the amount of water present in the planet's climate system.

For planets in more circular orbits, ie, that formed around the red dwarf, we are limited in how massive we can make that planet the same way we are limited with gas giant moons, in this case topping between 2 to 10 Earth-masses, which we could actually distribute in a planetary system of Terran and Subterran worlds which suffer from the same condition, but varying climates according to their specific atmospheres, water content, and distance from the red dwarf.

2:1 case, system must be smaller than 0.22x the orbital separation

A ~ 1.00 Msol, 1.00 Lsol, 1.00 Rsol, 5778 K - G2V yellow dwarf

    Mean HZ for A: 1.00 AU

B ~ 0.50 Msol, 0.10 Lsol, 0.57 Rsol, 4334 K - K6V orange dwarf

    Mean HZ for B: 0.39 AU

Now because our habitable zone around the secondary component expanded to double the previous orbital radius, we have to change the distance between the stars just a bit to accommodate those changes. So the system's minimum size, given the planet has to orbit within 22% of the orbital distance, is about 1.82 AU, orbiting every 2 years. This way, the star's hill sphere is about 0.8 AU in radius, snuggly fitting our habitable zone at 0.4 AU, and given our parent body is larger than the previous one, our planets can be up to 6 Earth-masses in size, even giving space for superterran worlds in orbit.

At such distances from the stars, the planet gets 0.63x and 0.30x the solar constant from its parent and the brighter star, respectively, being close enough to barely rotate instead of being tidally locked. Its equilibrium temperature is around -24°C, and it warms up to 10°C under 1 Earth-atmosphere. By setting the planet's rotation to 500 hours the equator is able to heat up to some 23°C.

When the planet is between the stars, the orange side drops down to -17°C and -4°C on the equator, while the yellow side to some -50°C.

We can already stop right here, as it was concluded from the last example and from the last post that trying larger stars help, but not a lot because of the greater distances involved.

DYING BINARIES

It is not (observationally) uncommon for a bright star to have a dead or almost dead companion in a binary pair, see the Sirius system, an A-type white star and its white dwarf companion Sirius B. However, since the Nova which forms a white dwarf most likely destroy the planets around it (if any survived the red giant phase) is too dim to provide any significant illumination, we will be looking at red giant pairs.

If we want planets in those systems to be habitable for a long time, then such systems would have to be either very old and originating from sun-like stars, or very young containing a sun-like star and a heavier pair. Whatever the case we choose, it will be composed of a star still in its main sequence, and a bright red giant. For the distances we can be somewhat liberal, alerting only for the absence or presence of planetary disks. Let's say that by the time our primitive planet starts developing complex life, our heavier star finishes its MS phase and starts diving into the red giant phase. A sun-like star spends two billion years in the red giant phase, with variable luminosity as time passes, very variable in the last few hundred million years, which means such worlds are pretty ephemerous. Let's use that as a basis, with a star that enters the sub-giant phase at the age of 4 billion years, setting the system's age half-way through the process. The chosen mass ratio is 5:2, still close to your typical common binary system.

A ~ 1.28 Msol, 2.47 Lsol, 1.22 Rsol, 6566 K - F5V yellow-white star (nominal stats)

Mean HZ for A: 1.58 AU

SUB-GIANT STATS:

Current Age: 4.48 Gyr, 400 million years until the Helium Flash.

Current temperature: 4000 K, it will continue to drop to 3000 K until the Helium Flash. 

Current luminosity: 5 Lsol, it will continue to steadly rise up to 25 Lsol, before taking off to 2500 Lsol for the Flash in a short period of 100 million years.

Current radius: 2 Rsol, it will steadly rise to 10 Rsol, until inflating to 200 Rsol (1.9 AU) when the Flash happens. 

Mean HZ for L ~ 5.0 and L ~ 25.0: 2.2 AU and 5.0 AU

B ~ 0.50 Msol, 0.10 Lsol, 0.57 Rsol, 4334 K - K6V orange dwarf

    Mean HZ for B: 0.39 AU

Just so we keep the secondary pair, and thus the planet, under a significant illumination from the dying star, the orbital distance will be about 3 AU. So as the ages pass, the planet will go from receiving 0.5 to 2.8 solar constants from the dying star, while getting a consistent 0.6x solar constants from its parent, so the total illumination will rise from 1.1 to 3.4 over the course of 400 million years. Under 1 Earth-atmosphere, the mean temperature rises from 22°C to 105°C over this period, staying about 20 degrees hotter than those in the equator. The coldest tropical nights in such a world simmer at 65°C, while the planet is more temperate towards the tropics, however, with such high temperatures, we need to make this a waterworld to buffer it all, or a dry rock so the clouds don't start a runaway greenhouse effect. We could also balance the temperature by smaking the planet smaller, which decreases air pressure and volcanism so we don't turn this world into a venusian right away. A half as thin atmosphere puts the planet on pair with the previous world even on the hottest phase of its life.

By varying the amount of water in the atmosphere and a little bit of the secondary star's eccentricity around the main component, we can better control the surface conditions, still obeying the same principles as before, though we now know such worlds will be flash burned when the subgiant becomes a red giant, elevating the mean temperature to about 850°C.

Given what we know from how atmospheres react to the incoming light of different stellar spectra, it is safe to say that once the insolation coming from the red giant exceeds 0.7~0.8 solar constants, the planet will be no longer habitable, for the amount of infrared the atmosphere receives can no longer be irradiated away to space efficiently, thus, the surface temperature rises several dozen kelvin for even the tiniest increase in luminosity.

Reproduced from Habitable Zones around Main Sequence Stars, JF Kasting et al, 1993

We can say for sure that our planet around a red giant won't be habitable for much longer than half of its life between main sequence and the helium flash.

Hence why whenever I set up a planet around red dwarfs I try to keep their insolation below 1.0 and above 0.5, one can go even lower if they wish to add brighter stars to the system, if those stars are considerably hotter, even a few percent more incidence will the job at illuminating and heating the planet up without tipping it over the edge of a runaway greenhouse event.

Though I admit a future me or one of my readers will eventually find something I overlooked or winged for sake of argument for this post series, after all, this is supposed to be an expositional guide, an exercise for you to explore other particular variations more invested than I was with those quick examples.

DO NOT GO GENTLE INTO THAT GOOD NIGHT

Ah yes, luminous black holes and their blanets (yes with a B, that's a thing). For the ones not familiar with the concept, it's the kind of scenario as presented in the movie Interstellar (2014), but for the ones not familiar with the inner workings of such systems, I must warn such systems in nature would be so rare and ephemerous that one might as well regard them as legendary oasis, from what I could find and understand.

WHAT KIND OF BLACK HOLES ARE SUITABLE?

Black holes are a very interesting class of objects for their extreme variety of sizes and surrounding structures. The smallest black holes are created by stars above 23 solar masses, when their core collapses at the end of their lifes, compressing a good chunk of its matter into an infinetly dense point, at least some 2.9 to 3.0 solar masses, the infalling material and subsequent radiation burst ends up bouncing back up and eventually spewing all of the star's upper layers away into space, hence why the resulting black hole is rather small compared to the star's mass. Such small black holes are called Stellar-mass black holes, for they have the mass of typical high-mass stars, and typically, those black holes are the most dangerous for civilizations, for they are very small to the size of a few dozen kilometers, zipping through space at stellar speeds, gravitationally interfering with other systems as they fly by, and worst of all, they are often very dark - because the are rather small, it is very easy for matter to orbit and catapult around it without getting even a tiny bit close enough to be shredded or absorbed into it, thus they rarely emit or posess detectable signatures but the light-bending their gravity produces.

Stellar black holes are also much more aggressive than heavier ones for their small size, with a virtual density much higher than massive black holes, that is, the density you would expect if it was a solid object the size of its event horizon - a person standing 100 event horizon radii from a 5 Msol black hole would experience a gravitational gradient between their head and feet of ~750m/s, leading to instant material failure of the astronaut and resulting spaghettification. Whereas this same configuration with a 1000 solar mass black hole causes a difference of only 0.02m/s, far more tolerable.

Massive black holes are gentle giants.

Larger stars produce large black holes nearly twice the mass of these, but since stars rarely exceed masses above some 50~100 solar masses, stellar black holes cannot get any bigger than some 10 solar masses. From this point onward things get strange, black holes can only get bigger by absorbing lots of matter and other black holes, which means that the larger black holes are often much ancient than most stars, planets, or even the galaxy it currently inhabits.

When we look at massive black holes and supermassive blackholes, those which range from thousands to millions of times the mass of the Sun, we often find those which are surrounded by large disks of infalling matter, accretion disks. As matter accelerates towards the black hole, it rubs against other infalling molecules, heating up to thousands of degrees, generating all sorts of radiation, including light - those are the Luminous black holes. Non-luminous black holes include the ones such as Sagittarius A* at the center of the Milky Way, with 4 million solar masses, it has barely any accretion disk, existing in the dark, puppetteering nearby stars around a seemingly empty region of space. The feeding rate of a black hole, or accretion rate, is limited by its Eddington accretion limit, which is how much mass can fall into the black hole, before the resulting radiation pressure of the accretion disk counteracts the gravitational force of the infalling matter, the brightest luminous black holes such as quasars, blazars, and young radio galaxies find themselves near this limit or at super-Eddington limits, when the black hole also absorbs the extra radiation it would emit despite greater accretion rate. For obvious reasons, blanets and stars cannot reside near such monsters, because they would quickly be disintegrated into the accretion disk.

However, one detail we have to pay attention to while looking to settle black holes with habitable conditions, is that for most of their life, black holes will exist in their dark form, while luminous black holes are rather ephemerous. A single black hole might go through several luminous phases along its life, feeding on unlucky stars for a few million years, then waiting in the dark for the next prey, hence why radio galaxies are always young, as their central black holes did not have enough time to clear their surroundings, so not yet in their dark phase.

The amount of radiation released from a luminous black hole is directly proportional to the infall of matter, sometimes a black hole will traverse a region of space with little more gas than usual and shine very dimmly with a ghostly echo, or sometimes a whole rogue planet falls in, quickly spaghettified into a bright accretion disk which, like the rings of Saturn, will last a few million years.

Because we want blanets, moons, maybe even other stars around our luminous black hole, the gas around it which is the precursos to all of these bodies will be likely of solar-composition, with some sprikle of metals and not only hydrogen gas like the interstellar medium. The black hole would have to be near the end of its feeding / luminous stage, as we still want an accretion disk as energy source, but not so large of an accretion disk it just disintegrates any rocks with dense x-rays. So if the Eddington limit says the max accretion rate is a few billionths of a solar mass per year, then we will lean towards trillionths of a solar mass per year.

Because the surface area for an accretion disk around such black holes is immense, many times that of whole stars, the surface temperature of the disk should be star-like, between some 6000 to 2500 K, this works out to quite a headache of math when you're not familiar with the principles or equations behind it...

THE GENTLE GIANT

For an Interstellar-like scenario, we'll use a supermassive black hole about 100 million solar masses, spinning at 99.995% the speed of light, an ancient monster which hasn't fed upon anything for many millions of years, just now licking the breadcrumbs of its plate, that is, with a very thin ghostly accretion disk.

We're talking a 1.0 AU radii event horizon, with a disk that extends from 1.3 to 2.5 AU.

Our Eddington luminosity is around 4~6 trillion solar luminosities (depending on the gas makeup), with an accretion rate of 2 solar masses a year. So if we want the disk's Earth-like insolation zone to be at around 3 AU from the monster, we need an effective luminosity of 9 solar luminosities. So now we divide 9 by 4 trillion, we then get 2.25 trillionths of 2 solar masses, or 0.00012 Moon-masses a year. With a temperature between 288 thousand K near the ISCO down to 83 thousand K near the edge.

Even though the temperature is not enough for hard X-rays to be emmited through the ionization of metals within the disk, most of its emissions are still in the far UV spectrum. This can be avoided by increasing the opacity of the gas, making it partially ionized in a wider disk or toroidal cloud around the black hole. This makes the inner rim of the disk extremely hot while keeping the outer parts of the disk less hot, which means we need to lower the metal content of our gas cloud, or else the breaking radiation of relativistic electrons will increase the x-ray output of our accretion disk.

As for planetary formation around such objects, it would boil down to general rules of planetary formation, except the progenitor gas cloud would be the spewed guts of one or more stars devoured by the black hole, which for our purposes would have to be the black hole's last meal in a long time, or else the extreme x-rays would just photo-evaporate our blanets.

Those conditions will be very rare or even impossible to accomplish in real life, like, even a small rogue asteroid coming from interstellar space and falling in would increase the disk's luminosity by orders of magnitude - frying whatever life existed in the blanet surface. In the whole universe with its countless blackholes there might exist very few of those legendary oasis where conditions are just right, where life is possible hanging from a silk thread.

Because photon-matter interactions are rather too complex to bother going through, I'd admit handwaving most of them away would be the best course of action - for the sake of story telling, the habitable zone distances and time dilation regarding proximity to the black hole would have way more weight to it.

But realistically, given the many unknowns regarding radiation tolerances, a habitable blanet would look like the following:

Assuming the event horizon is some 10° wide in this image, the planet would find itself at 6 AU, receiving 1/4th of the Earth's insolation.

Would that be enough? I don't know, my IR correction equations are calibrated for stars, not massive accretion disks, the output for this case is right at the face of the event horizon inside the disk's inner radius, at 1.2 AU

An icy/oceanic superearth far far away from the black hole, some 10 Earth-masses and between 2.0 and 2.5 Earth-radii, the illumination is pretty dim compared to Earth's, but the incidence of x-rays and electron wind against the thick hydrogen/helium rich atmosphere reacts to produce scattered radiation, which warms it up to a tolerable temperature between 200 and 400 K. The atmosphere however would be rather anoxic, as the rays cannot penetrate very deep to react with the water or ammonia which pools on the surface as oceans, and any bacteria that develops here would be anaerobic, feeding on high energy or infrared light rays and minerals dissolved in the oceans, in a way, similar to Miller's planet - except much dimmer, much redder, and warmer.

For flavor we could add our habitable planet as a moon of a gas giant, or the more unlikely case - as the tidally locked planet of a red dwarf, working pretty much the same way as the first example from the start of the post, which seems to be the only viable way to obtain the desirable Crematoria-like effect

- M. O. Valent, 13/02/2023