Little is known of the ferocious she-demon known as Nysuss, other than she is a demigoddess and came to Graxia from an unknown hell-plane. Many suspect that she's the Destroyer of Worlds and has come to Graxia to oversee its final destruction.
What is known is that Nysuss was summoned by a secret clan of mages. They once belonged to the Sunspire Clan, but when they dabbled in the forbidden arts, they were exiled and forced to live at the bottom of the Eternal Pool.
The summoning of Immortals gave them an opportunity to reassert themselves in the world and exact their revenge. All they care about is path of death and destruction that Nysuss will sow across Graxia.