Machinations of the Slave Lords!
Tharizdun is a legendary deity whose name has not been heard for millennia across Oerth. His nature and goals are shrouded in mystery and terror, but now his cult has resurfaced once again, and have become a terror to the lands surrounding the Azure Sea.
Also known as the Elder God, the Elder Eye, the Elemental God and the Elder Elemental Eye, Tharizdun is a god of entropy, chaos, destruction, betrayal, madness and undeath. He grants power to all those who ask, but just as quickly withdraws that power. His true form is said to be that of an amorphous, black, undulating, tentacled mass that exists in the space between spaces, the darkness outside of creation, a legendary realm known alternately as the Far Realm and the Outer Dark. He is a god of outcasts, of misfits, and of all those with murder in their hearts.
The Cult of Tharizdun
The resurgent cult of Tharizdun appears to be comprised of exiled drow, the goblinoid and orcish races and corrupt humans. Their goals are world-spanning; they seek to resurrect the ancient, lost empire of Netheril and spread their influence across Oerth.
For more on the Cult of Tharizdun, see this archived article at Wizards of the Coast. As with everything in my campaign, I may and will change any and all details of “official” canon as I see fit.