Sedna was a sea spirit revered by the Koyukon. According to their mythology, the creatures of the sea were formed from her body when, betrayed by her father, she drowned and sank to the bottom of the sea. She become ruler of Adlivum, the land of the dead.
Gaborik believed that the hybrids which attacked Nyssa were Sedna's familiars, seeking revenge for Shaun Brett's desecration of the land. When Brett and Tulung fell under the Permians' influence, they also came to believe that the creatures were spirits. (AUDIO: The Land of the Dead)