I had an idea for a movie/novel/something recently, and I thought since there's a low chance of it ever actually becoming anything, I'll post the idea here and let your guys play around with it and maybe make it better.
To put the idea in summery;
Tyranids invade the Earth. (not the one with the Emperor on it, the one we're on right now. I have a few ideas to explain that which I'll detail later) Global apocalypse ensues. Since a story about everyone dying at the claws of tyranids would probably seem a tad bit pointless, I've thought of a few ideas for a small group of humans (or a large one) surviving to escape/repel the invading Tyranids, which are as follows; (I don't want to simply have ZOMG SPEECE MEHEENS, as the space marines are waaay overused)
1. An ancient and mysterious cult worshiping the Chaos gods rises into prominence in the chaos of the invasion, promising unimaginable power and salvation from the tyranids. I like this idea, though I don't like it as the only Deus Ex Machina, rather as a secondary antagonist party which may crop up again if there's a sequel.
2. Eldar, foreseeing the rise of the Chaos cult, seek to guide the humans away from the path to corruption, also helping them escape the tyranids through ancient webway gates on the moon. However, why would they go through such bother and risk for some primitive feral humans when they could so simply just blow the whole planet up?
3. The Tau, seeing the impending doom of Earth as an opportunity to bolster their ranks and enlighten another species to the truth of The Way, help the humans flee from the tyranids and assimilate them into their empire. I have two problems with this, one being that I've heard that the Tau have a way of 'assimilating' with orbital bombardment, castration and concentration camps, the other being that it sounds too much like the "ZOMG SEECE MEHREENS" I'm trying to avoid. Plus, I think some of the other options would leave room for a more interesting sequel.
4. We make our own getaway with conventional/stolen/Chaos technology.
Also, for explaining how the inhabitants of Earth have been isolated from all the other factions, I have these;
1. Failed colonization attempt by the Imperium which nobody cared enough about to help.
2. Chaos did it. (See wut I did thar?)
3. A small group of humans way back accidently teleported themselves here, then proceeding to progress into today's society.
And that's it. Let the lore-nut rants begin!