>>227575
Even better, steal from Ascension.
The Hollow Earth exists, and unlike the other Spirit Realms, it's reachable by normal humans. Whether you dig too deep, or you explore an ancient endless cave, or you go down an unremarkable elevator, or even a flight of rickety stairs, it's possible to enter the Hollow Earth. That's what makes it fucking scary - anything leading down might take you there.
Once you reach it, you're going to run into dinosaurs. And mammoths. Cool, right? Except somehow, everything long gone manages to end up here - and that includes eldritch abominations, horrors from beyond and so on. Things that should've died aeons ago. Secrets best kept buried. And yet here they are, alive and kicking. And angry.
Oh yeah, and every ancient civilization also somehow managed to get down here. Atlanteans, Shambhalans, all of them and more. All of them decked with arcanotech that makes the impossible possible. And to top it off, the Nazi occult division is around as well, experimenting with ancient technology and dinosaurs.
And of course, you can step up and join them. Or fight them. Or forge your own empire.
Have I mentioned Ascension is awesome? Because Ascension is awesome.