Men of 13 races fight for life and power, ignorant of their common past.
When other tools fail, foul sorcery is wielded without compunction,
Enigmatic and inhuman space aliens have crash-landed on the world.
Psionic warriors turn the tables on uncaring Great Old Ones with strange technology from the stars and beyond Time's provenance, risking blasphemous madness and worse to tame the hostile planet and push back the darkness if only for a little while.
Carcosa is a science-fantasy role-playing game setting with a sandbox approach: whether heroic or opportunist, adventurers of all stripes will find freedom and consequence worth their mettle in a horrifying milieu mixing adventure fantasy, the Cthulhu Mythos, and comic book SF with no punches pulled.
Carcosa is compatible with Lamentations of the Flame Princess and other old school fantasy adventure games. This expanded edition details 800 encounters on the 400 hex map and includes the starter adventure Fungoid Gardens of the Bone Sorceror.
Here's what Jim the Publisher had to say about it.
Geoffrey McKinney, the author, has also written Isle of the Unknown, another old-school setting which has less horror, but retains large amounts of weirdness.