Tharizdun

Tharizdun is a long-forgotten interloper god who seeks to destroy all that is. During the Dawn War he was imprisoned in a remote layer of the Abyss, from which his followers hope to set him free.

Background
A deity hungry for power found and seized the shard of evil. This god, Tharizdun, found his mind and spirit opened to the obyriths trapped in their dying darkness. The link to those foul beings corrupted him in an instant, driving the deity to madness. But the obyriths' plan to seize the celestial realms controlled by Tharizdun and his kind was met with resistance and a twist they had not anticipated. The obyriths demanded that the deity plant the seed of evil within the Astral Sea, promising him total dominion of that realm in exchange for his fealty. Even within his madness, however, Tharizdun recognized that his fellow gods would turn on him before he could fully seize the power the obyriths promised. Instead, the mad god traveled to the farthest reaches of the cosmos, planting the seed of evil in a primordial expanse of the churning Elemental Chaos, the realm of the fallen primordials, which he hoped to seize as his own.

History
In 1340 DR, a cult of Tharizdun formed in western Chessenta. It hired bandits, consorted with demons, and caused much havoc before an alliance of forces destroyed it. Some credit the fact that Tharizdun did not gain a permanent foothold on Toril to the personal intervention of the goddess Mystra.

A new cult of Tharizdun was formed by the plague demon Murmur in 1479 DR after a burnt portion of its corpse was discovered by the Firestorm Cabal in Akanûl. It possessed Leheren, one of the members of the Cabal, and created a secret order within the order devoted to freeing Tharizdun and releasing him on the continent of Faerûn.