2-5 minions of evil ancient deities come together to attempt to break the seals keeping them at bay and awakening them in 3 Rituals (rounds of play). Typically this is done by "following the suit" of play, with a twist. If everyone plays ritual chant cards matching the current "spell", everyone gets a point. If, however, someone differs, committing an 'evil act' against the others, the one who played the differing chant (least in kind) ALONE gets a point.
BUT...if everyone plays a different chant spell, you gain Insanity. 3 insanity points and you are out.
One last twist: If everyone IN UNITY plays the same kind of spell chant that is different from the needed spell, you all get a point.
No communication is allowed between players, you just have to use your wits to determine what you will do...
—description from the publisher