So I've got this superpowered mutant superweapon created by some metallic race. It was meant to devour life on worlds in order to clear out areas for colonization, but stuff went wrong and it escaped and regained sentience and decided it would rather go on adventures and make friends(it still has to eat a lot to sustain its high energy needs enough so it won't revert into an uncontrollable ravenous monster). It goes into a hibernation state when traveling between solar systems.

At first I decided it would use energy derived from animal life(or high energy foods because it doesn't want to be a murderous superweapon) to convert to matter to repair itself(it's made of elements from a neighboring universe so using the elements found in the home universe wouldn't work). Then I found out that it takes an absolute heck ton of energy to make matter.

So unless I can figure out how converting normal energy into some magical energy(magic does exist in this universe) and then the magic energy into larger amounts of matter than regular energy-to-matter conversion would get you might work(anyone with ideas let me know; I'd rather something like this actually), it would need to be able to convert matter into energy and then into usable elements.

But then how could it be prevented from consuming entire planets into its pocket dimension stomach if it wanted to? It would store energy in pocket dimension containing micro crystals throughout it's body.

Maybe a solution would be that it can transfer organic matter into energy easier than inorganic matter? But then why and how would that work?

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    $\begingroup$ It seems to me you answered your own query: It's a sentient creature. It simply decides not to consume the entire universe. $\endgroup$
    – elemtilas
    Dec 30, 2019 at 1:51
  • $\begingroup$ This seems very similar to the plot of Final Space. $\endgroup$
    – user535733
    Dec 30, 2019 at 2:07
  • $\begingroup$ @elemtilas but it's creators would not know it would regain sentience, so they would have had to have something in place to prevent it from going beyond what it was supposed to. $\endgroup$ Dec 30, 2019 at 4:06
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    $\begingroup$ I'm missing something. If it can convert, say, a thimble full of cat-litter into energy, can it not convert that into an equivalent mass of fictional elements? Even if the thing is ultra dense, there are places that would PAY this critter to consume several tons of things better left not lying around. Instant solution to nuclear waste. $\endgroup$
    – user8827
    Dec 30, 2019 at 6:32
  • $\begingroup$ @SeanBoddy that's the plothole I'm trying to figure out. What would keep it from eating things other than the life it's supposed to clear out? $\endgroup$ Dec 30, 2019 at 20:48

2 Answers 2


In our universe, energy and matter must be conserved, even if they are called 'magic'. Regardless of the high ratio of energy to matter (presumably you are referring to Mass Energy Equivalence, or E = mc2) this is a guiding principle of physics that no information is lost, energy is simply converted from one form to another, and that mass is actually energy and vice versa.

If they are not conserved, then you have the ability to either destroy matter and energy, or to create them at will. This yields deeper problems in your alternate universe, as you mentioned this ability can cascade and snowball into big problems:

  • Creation of infinite amount of matter, or an infinite universe, or universe of infinite energy, given sufficient time
  • Destruction of the entire universe

How do you stop this? Introducing equivalence is a good method, which tends to provide stability. There is a reason why galaxies, stars and planets form in our universe, why there are limits to their physical size and number, and take the form they do.

A current day star is a balancing act between matter and energy, too much one way and it would expand and explode, too much the other and it would collapse. Your sentient being might have similar constraints.

By converting a planets mass into energy, your being has equal amounts of problems containing that energy. It could be difficult to handle, store or manipulate. It needs to be balanced in order to retain its form, shape or size.

  • $\begingroup$ Magical pocket dimension containing micro crystals throughout it's body store as much energy as it wants. $\endgroup$ Dec 30, 2019 at 4:09
  • $\begingroup$ The conservation law is something I'm trying to figure out. Maybe there's some magical chain reaction with something that multiplies the energy? $\endgroup$ Dec 30, 2019 at 4:22

Travel time will limit the creature’s reach, just as it limits the reach of all creatures and technologies. If it starts at Earth, will take centuries just to get to the twelve nearest star systems.

Further, both energy and matter is sparse in the void between stars. So it might starve to death as it travels.

Space is big. We keep stressing that on this website, but it bears repeating. Whatever your plot, the stars span a greater distance than most writers can fathom.


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