The Skull Raiders were an ancient group of pirates who plagued the island of Okoto in the years prior to the Battle of the Mask Makers. After a conflict of unknown duration, they were driven into one of Okoto's mountain ranges by Ekimu, Makuta, and the Protectors of the time. However, Makuta later sought out the raiders and forged an alliance with them, in which their leader Kulta pledged his service to Makuta. The cataclysm unleashed by the destruction of the Mask of Ultimate Power caused the cave in which the Skull Raiders had taken refuge to become buried. They eventually dug it out and constructed their own city beneath the mountains, with Kulta digging a tunnel that allowed him to exit the underground metropolis.