Zzeraku and his companion Valoku were two nether dragons who spent most of their time hunting for prey in the vicinity of Hellfire Penninsula prior to the reopening of the Dark Portal. They were well known to a tribe of Broken whom were often the targets of their hunt.
Shortly after the surviving demons of the Third War under Lord Kazzak managed to reopen the Dark Portal and reunite with their kin on Outland, prompting the investigation of Tyrygosa, a blue dragon, one of the caretakers and investigators of magic. Zzeraku and Valoku came across Tyrygosa after she had been struck down by the Death knight Ragnok Bloodreaver. Tyrygosa recruited the help of the two nether dragons in locating her missing companion Jorad Mace but was mislead and attacked by Zzeraku before he flew off abandoning her.
After Tyri and Jorad were reunited they gave chase but were once again confronted by Ragnok and his band of minions. Jorad had been thrown from Tyrygosa's back and she was nowhere to be found when Zzeraku reappeared and for some unexplained reason carried Jorad back to the relative safety of the broken camp.
At some point after, Zzeraku was one of many nether dragons that swarmed through the Dark Portal into Azeroth upon the portal's reopening. The blue dragonflight met the invaders and destroyed every last one, confident there had been no survivors. But Zzeraku had been taken captive without their knowledge. The former consort of Deathwing, Sintharia, had used a crysalun chamber to trap the wayward nether dragon. ( )
Sintharia, now calling herself Sinestra, little by little fed the nether dragon to her newest creation, the twilight dragon Dargonax. Zzeraku, immobilized deep within Grim Batol, suffered greatly but refused to have his will broken. He was inspired by the draenei priestess Iridi's attempts to free him, and flew into a rage when he saw harm done to her - breaking free of his bonds and engaging the twilight dragon in a battle that led them out of the halls of Grim Batol. There, Dargonax fully absorbed the dying Zzeraku, who had decided to try and save Iridi at the cost of his own life. His sacrifice was not in vain however: He catalyzed the minor defective part within the twilight dragon that Iridi and her allies were able to exploit and finally defeat Dargonax.