Setting: An Earth-like planet except all the continents are joined together like Pangea. The locals are in the medieval era and have the ability to use magic. Magic can level buildings at best, certainly not enough to leave the planet.

Population: approximately a million humans, a million elves, a billion demons, and all the other kinds of plants and animals

Problem: A super eruption similar to the ones that happened during the Earth’s Permian period. It will cover a quarter of the continents in 50 meters of lava. Any continents that aren’t reached by the lava will still be affected by ashfall, sulfur monoxide and the blocking of the native sun.

Would be saviors: 250 genetically modified, immortal humans with an intelligent AI who were transferred to the planet when their universe decayed. They too have a tech level of the medieval era as they still have to develop technology.

Preparation time: Approximately 220years, though the area that’s about to erupt is already experiencing release of steam and explosions which is how the human saviors found out about the coming eruption.

Goal: To save as many as possible.

Ps: The humans from the other universe can’t use magic so they can’t transfer the lava to the old universe. I was hoping they’d develop tech to interplanetary? or interstellar which ever works.

Also, this past question of mine goes into detail about the AI and the humans. How long or how hard is it to develop a medieval fantasy into a modern or even sci-fi civilization.?

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    $\begingroup$ You should really define the scope of your magic, since that's the only chance they'll have without technology. $\endgroup$
    – Muuski
    Feb 14, 2020 at 15:43
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    $\begingroup$ If you're wanting a non-deus-ex-machina solution that is both clever and not made of concentrated plotonium I dont know what to tell you. You've already listed an ability to casually transfer to a new universe. Transfer the superfluous lava to the abyssal plane (probably why it's so abyssal) or even to your ex-wife's front porch. Transfer everyone to 1 million years in the future. If these AI are intelligent, and they understand how intelligence works (they are AI after all), have them upgrade themselves to minor gods and fix things. $\endgroup$
    – John O
    Feb 14, 2020 at 15:44
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    $\begingroup$ Why evacuationg planet would be easier than putting "teleport" on eruption and evacuating it into some planet? $\endgroup$ Feb 14, 2020 at 15:46
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    $\begingroup$ @user72381 dunno, You could make w hole novel about 200 years of looking ways to evacuate planet because the Winter is coming and then finish with a plot twist - The Winter is the one who get evacuated. $\endgroup$ Feb 14, 2020 at 15:57
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    $\begingroup$ This doesn't sound like a worldbuilding problem; this sounds like "help me write my plot." $\endgroup$
    – levininja
    Feb 14, 2020 at 17:09

2 Answers 2


Frame Challenge: Your post-catastrophe planet is still more hospitable than "space." Without a specific, already-habitable destination, getting the people off of the planet is just one of a whole family of problems. "Good news! We've figured out how to get you off the planet, so you can escape the coming catastrophe of fiery lava, endless winter, poisoned air, and poisoned seas! The bad news being that your destination is a frigid, airless, radiation-blasted void which will kill you almost instantly."

We're not talking a temporary evacuation, either - the Permian-Triassic extinction event may have left the planet fairly inhospitable for millions of years. Wherever you're putting your people (and elves, and demons), it better be effectively permanent! Well, maybe not from the point of view of the immortals, but from the point of view of your evacuees.

You're seriously better off with your populations trying to eke out some kind of existence on a poisoned world than flinging them into the inhospitable emptiness beyond. Maybe magic can't boost you into space, but if it can purify the air and keep a little bit of food growing...

IF you had the science-fiction technology at your disposal which your scenario hasn't supplied yet, all manner of possibilities would present themselves:

Gray Goo, in a good way

Nanotech (or other exponential recruitment of resources)

Building shelters for over a billion people to live in space is rough. Getting it done in 200 years is harder. Digest a chunk of the planet to quickly spin up shelters, rocket ships, whatever.

Why wait for the eruptions? Blow up the planet now

Whenever your space habitats are ready, if the assumption is that you're leaving behind the planet for good, why leave behind a planet? Getting over a billion people out of a gravity well, along with all their habitats and stuff, is a huge effort. The gravity well needn't survive the effort.

On the other hand, assuming that level of technology and resources, you might be able to head off the eruptions altogether, and save the planet. Or at least just leave sealed habitats on the surface. The real downside to just staying on the planet at that point is little to no free solar power.

On the other hand, why save everybody when you can "save" everybody?

This might almost be possible already (depending on the properties of your AI). Forget evacuating the planet. Forget finding a way to keep everyone alive. Make digital copies of the world's population. Wait out the extinction event. Use advanced tech to reconstruct them afterwards.

It will be interesting, with explicit magic, to address how this will work with souls (or retention of magical powers, for that matter).

  • $\begingroup$ That last bit of yours is a moral dilemma... Sci-fi humans might get PTSD(?) from killing an entire planet off only to repopulate it. $\endgroup$ Feb 15, 2020 at 14:30
  • $\begingroup$ I think the population could be put on biospheres on the other planets of this solar system. I realize that what I just said is pretty difficult lmao. $\endgroup$ Feb 15, 2020 at 14:32

The way in is the way out.

However you choose to get your immortals to the planet is how you are going to get your people off. There are a few reasons for this.

  • You have already established it is possible in your universe
  • Your immortals already know how to do this, so they just need to do it again, but with less time and resources.

So in this case, they will build a device or spell that allows them to transfer to a planet on another universe.

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    $\begingroup$ This certainly meets the Chekhov's Gun criteria. $\endgroup$
    – user535733
    Feb 14, 2020 at 19:56

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