Catari was a demon who served as the Qwa Ha Xahn of the Old OneIllyria during her rule. As the High Priest of the God King of the Primordium he was "elevated above all that live."
When Illyria was destroyed and sent to the Deeper Well, he begged for mercy to theOld Ones that destroyed his master, they sealed him in the North Pole, to defend one of the three Icons of Illyria.
When Illyria arrives with Liandra, she demanded the return of her icon, but he refused, betraying her, because if he surrendered the icon he would die. After a short battle, both killed him, his body falling to the depths of the Artic Ocean.
Behind the Scenes
As he appeared in a crossover, his canonicity is unknown, though most likely he is not canon.