The Grimorium Verum is an arcane book of mystical incantations.
Found within its pages is an alphabetized list of rituals used to summon demons. In 1978, John Constantine used the Grimorium Verum in an effort to summon the demon Sagatana. It was his hope that he could force Sagatana to destroy another entity known as the Norfulthing. However, John mis-spoke the incantation, and instead summoned the demon Nergal.
Links and References