Keeping with the intergalactic wordpress theme here…
Looking at the pathfinder sorcerer bloodlines – in particular, the voidtouched wild lineage starsoul mutation thing – it strikes me how well the concepts of necromancy and space travel fit together. I’ve toyed around with it a little in writing, having stuff like an academy of necromancy on the moon, making part of the lichdom ritual to experience the suffocating blackness of space, so on and so forth. It’s crazy though, how well the theme of spaceships and necromancers or summoners interface with each other.
First consideration is the fact that you won’t need life support. You don’t have to breathe if you do some kind of become undead ritual, and even if you do, your undead don’t. No atmosphere, no food for them, maybe your only problem as far as life support is concerned would be gravity. So you could just program your undead army to fly the ship, put yourself into cryogenic slumber and have them awake you when a suitable planet-sized body of solid material with an atmosphere is found. Of course the options only broaden if you don’t treat undead as… basically, computers.
A more outlandish idea would be some kind of reanimated organic ship. Whether by harvesting a bunch of spines from a bunch of creatures, binding them together and reanimating them, or modifying and crawling around in the inside of a giant dragon (you’d be working with something larger than a blue whale, and you can already get someone to crawl around in the intestines of those) you could probably rig up a sentient starship like this. I’ve always thought necromancy was a bit undeveloped in stuff like Dungeons and Dragons, because you can raise all the corpses you want, but I don’t think it ever goes onto grafting limbs and designing your undead minions. I’m thinking a ten-armed giant with a dragon’s head and the brain of a mindflayer, and his body covered in beholder eyestalks, or something equally overpowered. If you can animate a corpse, and you can animate multiple corpses, why would there be a problem with reanimating several parts of corpses stuck together, like a spaceship made from bones enchanted to endure the rigors of outer space?
There is a consideration, though: vampires. Vampires are, traditionally, affected by sunlight. Scientifically, the reason the sun affects them and not any other star, might be because it’s the closest star to the planet. But when you’re in space, you don’t have that kind of stability. an astronomical unit is the distance between the Earth and the sun, so if you plan on having vampires onboard, or if all undead are effected by the starlight, then you would have to stay at least one AU from all stars at all time, or risk severe casualties. This only gets worse if your ship is organic and all undead are affected, you might suddenly find yourself floating there, either asleep without hope of waking up, or without means of moving and so being trapped there, forever. Needless to say, that would suck.
How do necromancers control undead, anyway? Sure, magic, but how does that magic take shape. Do they manually operate groups of muscle and bone? Do they build some kind of grid across the corpse’s brain and trigger neural impulses? How does necromancy operate. What would stop you from making an organic supercomputer by meshing the processing power of a bunch of sustained brains together and hooking them up to some kind of external body like, say, a spaceship, or a monitor? Human bodies and, more specifically, human brains work using bioelectricity. I’m sure hundreds of them working together could generate electricity to power some kind of electronic device, or something?
The concept of the necromancer within a modern or sci-fi setting has always interested me. Not because of the undead army of apocalyptic doom, although that is a plus, but because of the weird interactions they could possibly be able to do. I mean if flying around the galaxy using a staff of greater teleportation, a ship of twisted bones enchanted durable and producing an gravity field, controlled by a skeleton crew (literally) and an AI composed from thousands of synchronized brains isn’t strange and awesome, then I don’t know what is.