N'Zoth

N'Zoth is one of the Old Gods nicknamed "The Corrupter" and an overarching antagonist in World of Warcraft. He is the Old God primarily responsible for the corruption of Nelfarion into Deathwing and is also speculated to be the one responsible for turning Queen Azshara into a Naga. He is currently the only Old God still active and rules the Nightmare from the depths of Azeroth's seas beyond the Rift of Aln, a location in the Emerald Dream linked to the Twisting Nether that is appears to be a reflection of a similarly-named massive chasm in the seafloor beneath the Maelstrom.

He was the first Old God imprisoned by the Titans after the death of Y'Shaarj when they discovered that killing the Old Gods could also cause the destruction of Azeroth as well, being sealed beneath the oceans. It's implied that he's actually broken his bonds, though he still received aid from Yogg-Saron and C'Thun in corrupting Deathwing provided they use Deathwing's Dragon Soul to escape Azeroth.