The group first encounters Sian and his two dog companions, Cer (ケル Keru?) and Ber (ベロ Bero?), as they are leaving the Regnum Cavern. There, Sian claims to smell Vritra, referring to her reincarnation, Hermana Larmo, who quickly distinguishes Sian as the reincarnation of the Manifest guardian Cerberus. Sian introduces himself before demanding to know where the Manifest is, claiming that since Vritra witnessed the destruction of Devaloka, she should know its location in Naraka.
His reincarnations are Sian Tenebro and Sian's two biological canine brothers, Cer (ケル Keru?) and Ber (ベロ Bero?). Each of these reincarnations derives from one of Cerberus's three heads.