Rituals are unique mystic rites that can be performed by practitioners of blood magic Disciplines. The vast majority of known rituals are those of the Tremere Discipline of Thaumaturgy, but other rituals exist for the Disciplines of Necromancy, Mortis, Assamite Sorcery, Setite Sorcery, Koldunic Sorcery, and other, more obscure forms of blood magic. There are many, many Thaumaturgical Rituals spread over many, many source books, although the ones most frequently referenced are those found in the Vampire core rulebook.