Sylok, the Defiled is a Taken Knight that was captured and imprisoned within the Prison of Elders. Following his capture, Reef technicians made several attempts to examine his mental architecture but were repeatedly and unconsciously compelled by his powers into psychically torturing him without being made aware of the compulsion.

Sylok both reveled in the pain and used it to feed his Worm. Sylok would survive his encounter with the Guardians and join forces with the Dread several years later. He would encounter the Guardians once again, who were seeking out Fikrul, the Fanatic within the now Tomb of Elders.