Zzeraku

Zzeraku was a nether dragon taken captive by Sintharia and used in her experiments at Grim Batol to create a new flight of dragons.

Outland
Zzeraku and his companion Valoku were two nether dragons whom 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. He is distrustful of many races, as the mortal races either try to kill or enslave his kind.

When the surviving demons of the Third War reopened the Dark Portal, Tyrygosa, a blue dragon, was dispatched to oversee the affairs of Outland on behalf of the Blue Dragonflight. 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.

Zzeraku encountered Tyrygosa again when she was later found investigating a Nether Dragon lair. From Tyrygosa, Zzeraku discovers that he and his dragonflight are decendants of Deathwing. They partake in the battle for the Dark Portal against Ragnok Bloodreaver's forces.

Following the defeat of Ragnok Bloodreaver's army, Tyrygosa attempts to free the enthralled dragons Ragnok enthralled but Kadavan informs her that those enthralled under his devices gradually weaken until they eventually burn out. Nothing can save them unless an extremely powerful source of arcane power can revitalize the dragons enough to free themselves. Tyrygosa, Kadavan, and Zzeraku open a portal to Azeroth and bring a group of enthralled Netherwing dragons to the Nexus where they absorb its magical energies. Yet Zzeraku and the Nether dragons grow mad with power, and frustrated with everyone they've ever encountered trying to use them, decide to be masters of their own destinies and conquer Azeroth for themselves. Tyrygosa tries to reason with Zzeraku, telling him that by following Deathwing's path, Azeroth will rise against them and lead to their destruction. Though conflicted with Tyrygosa's sincere concern for his kind, Zzeraku believes that only by gaining power can he safeguard his people. The Netherwing dragons attack the Blue Dragonflight, and in the midst of the chaos, Malygos awakens from his slumber. In his insanity, Malygos misinterprets the Nether dragons arrogant proclamations of being the embodiment of the Nexus and absorbs them and their power.

The dragon's Nether-warped physiology began to affect the Spell-Weaver himself, ultimately helping him regain some of his lost sanity. With his sanity restored to him, Tyrygosa's patron declared war on mortal spellcasters, sending his flight out to do his bidding. Only Zzeraku managed to escape, debating with himself whether Tyrygosa was right in choosing another path for the Nether Dragons that didn't involve aggression. Yet as he roamed Azeroth, he was eventually captured by Zendarin Windrunner who trapped him in Balacgos's Bane.

Azeroth
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.