Long ago, the Goddess of Light, Keitsuna, lived in solitude. The world she shared with Kadath, the God of all things Dark, was a void filled by Chaos. Then Keitsuna created the worlds of Sorla and filled them with creatures she took from other worlds. She also created the humanoid races that would live on each planet, and told them how to live on their own.
Not one to be outdone, Kdath created shadow worlds of Sorla. Again, Chaos interfered. The creatures of the shadow world are twisted shadows of the utopian worlds. After centuries of living in the darkness, banned from the light by those 'above' them, they have become hostile and bent on destroying Sorla.