Immortal: Invisible War
The premise is that human minds have a strange effect where they put any spiritual being they encounter into a human-like body. The world is full of spiritual creatures (some good some bad) that are stuck in flesh. When you leave Earth, either by going to outer space or a a spirit world, you are the spiritual being instead of a human. The players' characters are spiritual beings that sided with humanity against lovecraftian horrors, and are now stranded on Earth. This was a roleplaying franchise that became tortured as the publishing duties were passed around a lot. The entire core rules used to be available for free download from the owner's site, but that domain registration has since lapsed. Finding physical copies of and the books is implausible, though there are some archives stashed as .PDFs that were released by the owner after the lawsuits were settled.
This text was added because roleplaying games offer an unusual case in intellectual property law. Because the rule-books are sold with the intention that their purchaser will create derivative work. Everything linked here is presumed by the authors to be based on copyrights of a defunct company whose assets were bought by several later firms. We're just trying to continue with the fair use we were originally sold. We don't advertise these works in commerce. None of this material is directly copyrighted, however this material is often derivitave of other works. The nature of those works is that they must make allowances for purchasers to develop the material for small-scale non-commercial use. Reasonable use on a small scale is never a threat to the originating copyrights.