The Kal'gerion Notes tell of how Bilrach connected Gielinor to the demon's realm through his "portal experimentation." Upon seeing the true power of the Mahjarrat, Kal'Ger and his army pledged their allegiance to Zamorak and Bilrach. The lore story Daemonheim Asunder goes into further detail, describing the fight between the forces of Kal'Ger and Bilrach that convinced him to pledge allegiance.