Some monsters have a theft attack. These include nymphs and monkeys, who steal items, and leprechauns, who steal money. In addition, some major demons, high level liches, and the Wizard of Yendor will try to steal the Amulet of Yendor. The Wizard also desires your own quest artifact and the invocation items. For completeness sake, your quest nemesis and Vlad the Impaler occasionally steal back the items they were guarding. Strangely, magic cancellation does not protect against stealing attacks.