Evil High Priest is a worker-placement game in which the players take the part of priests of a Lovecraftian entity. All players worship the same Great Old One, but they are emphatically not allies. When they awaken their Great Old One, he will decide which among them is the best (based on VPs) and appoint that priest, and that priest only, to be the High Priest, who wins.

The Blood Ceremony Expansion contains 4 new Cult boards (Tcho-Tcho, Sleeper, Opener of the Way and Crawling Chaos), 1 Tcho-Tcho Growth Counter, 4 Crawling Chaos Avatar Cards, 12 Monster Cards, 10 Investigator Cards and 10 Priest Cards