Look at the bottom right pic. This is just a concept so it's not likely indicative of anything, but it brings up a cool question.
Something that has not yet been successfully done in games:
Can you make a subterranean species?
From a game design viewpoint. This isn't hard. All that's needed is for the game world to extend down in the same way that it extends up to the sky, but putting automatic barriers that line up with the ground
From a realism viewpoint. There are loads of subterranean creatures (most very small and very close to the surface) including moles and ants as the best examples. Examples like bats living in caves doesn't count, since they're not "underground" they're in tunnels naturally formed but need to move in open space and need to exit that cave. Sci-fi and fantasy are also littered with subterranean creatures (Morlocks being one of the earliest examples, if we're not to count Vernes' "Journey to the Center of the Earth", and Sandworms from Dune being one of the most common examples.)
Can we make a subterranean creature? And better yet, can we make a subterranean intelligent culture?
