N'Zoth is an Old God, one of several malefic beings that were sequestered by the Titans during Azeroth's primordial ages. N'Zoth is responsible for the "spark" that created the Emerald Nightmare. He is also the being that is largely responsible for Deathwing's corruption and current state. Millennias ago, Warlord Zon'ozz and his faceless soldiers waged endless war in the name of N'Zoth against the forces of C'Thun and Yogg-Saron.
Thousands of years ago, N'Zoth, Yogg-Saron, and C'Thun were The Three corrupters sparked the Emerald Nightmare. N'Zoth was the leader of the group,