Describes the cult of Lanbril, “a cult of the criminal underworld in human cities throughout the Barbarian Belt, in particular the Holy Country, Dragon Pass, and southern Peloria”, including mythos and history, iconography, life after death, the followers of Lanbril, the Way of Lanbril, common thieves, new common Thief skills, Initiate membership, special Thief cult spirit magic spells, Lieutenants (Acolyte membership), Master Thieves (Priest membership), common Thief cult divine spells, subservient cults, associated cults, and miscellaneous notes. Also describes joining a Thief Ring, on the job training, and changing Thief cult allegiance.