Shard of Evil
Before the Chained God brought this back from beyond creation, there was no evil in the world. There was no good, either. The gods and Primordials strove against each other over possession of the world, but neither side attached value judgments to the conflict.
The shard of pure evil changed that, creating by its existence the concepts of good and evil in creation. It polarized the beings in existence, as some chose one side of the new equation and some the other. The introduction of these philosophical differences almost shattered the alliance of gods, threatening the existence of the life and wonders they had created in the world.
As punishment for this crime, the Chained God was bound to the shard and cast into the depths of the Abyss for all eternity.