Tales of Tel'Palurin
The Godshield is a construct of pure Astral energy, the energy of the divine, that holds back the horrors of the Mere, and its most voracious inhabitants, the Primordials.
At the end of the Succession War, as the Godshield was being closed, the god Aragmar, for unknown reasons (possibly having been driven insane by the horrors of the war), drove a shard of elemental evil into the closing edges of the shield, releasing a cataclysmic chime of absolute chaos, an amalgamation of sound both beautiful and horrifying, the Discordant Melody. The shard, wedged between the Godshield’s closing edges, left a rift in the shield, a weak point. Fearful that the Rift would be exploited by the Primordials, the gods added a clause to the Succession Treaty, ordering that Aragmar be chained forever in the Abyss, forced to hold closed the rift he had created.