The Old God N'Zoth is represented in Hearthstone in various forms:
N'Zoth, the Corruptor - legendary minion card from the Whispers of the Old Gods set- N'Zoth, the Corruptor - legendary minion from the Wild Event set
N'Zoth, God of the Deep - legendary minion from the Madness of Darkmoon Faire set
N'Zoth - promotional warlock hero for the Madness of Darkmoon Faire set
See also
Tentacle of N'Zoth - common minion card from the Whispers of the Old Gods set- N'Zoth's First Mate - common warrior minion card from the Whispers of the Old Gods set