The OverLord of Light is referred as the co-creator of the world and the human race alongside his "twin" the OverLord of Darkness whom he was slayed by after the creation of the world and even though he is the co-creator he is somewhat similar to The Devil as being the one who leads humans to rebel against their creator and with the Agito as his Fruit of Free Will.
Long ago, the Overlord of Light coexisted with his "twin" the Overlord of Darkness as they created the world. However, when neither could agree on who would reign over their creation, OverLord of Darkness triumphed over his brother in the resulting battle. But in his dying breath, the OverLord of Light bestowed his essence upon humanity in the hopes that they would evolve beyond his brother's control. Refusing to allow such advanced humans to exist bearing his brother's essence to exist, the OverLord created the Lords to kill all humans who possess the potential to "evolve" into Agito while dealing with the Grongi Tribe who have been preying on humans for their game.