Shapeshifters were spirits who came to Ningen-do, willingly or by accident, from other Spirit Realms. Due to their connection to their realm of origin (Meido, Toshigoku, Gaki-do or Yomi, for instance), these spirits could in some way control their shape and appearance. Due to the return of many ancestors through Oblivion's Gate there was a ritual designed by the Phoenix Clan that could sever such a connection and make them fully mortal.