GURPS Horror: The Madness Dossier

GURPS Horror: The Madness Dossier is a campaign setting for use with the GURPS tabletop roleplaying game. The players take on the roles of operatives for Project SANDMAN, defending the world from the "irruptors", monstrous beings from outside our reality. The irruptors corrupt people into worshipping their masters, the godlike Anunnaku, with the goal of controlling enough psychic energy to alter reality and enslave mankind.

Links:
Official Site
RPG.net Game Index