Valoku and his companion Zzeraku were two nether dragons who spent most of their time hunting for prey in the vicinity of Hellfire Peninsula prior to the reopening of the Dark Portal. They were well known to a tribe of Broken who were often the targets of their hunt.
When the surviving demons of the Third War reopened the Dark Portal, Tyrygosa, a blue dragon, was drawn to Outland by a strange yet familiar source of magic. Zzeraku and Valoku came across Tyrygosa after she had been struck down by the death knight Ragnok Bloodreaver and was captured by a tribe of Broken. Valoku advocated that they help her as she was like them and could answer their questions but Zzeraku didn't trust her. An argument was sparked between the two nether dragons that distracted the Broken enough for Tyrygosa to escape. Tyrygosa recruited the help of the two nether dragons in locating and rescuing her missing companion Jorad Mace but was mislead and attacked by Zzeraku before he flew off abandoning her. Valoku flew off behind him.
After Tyri and Jorad were reunited they gave chase but were once again confronted by Ragnok's band of minions. Tyrygosa had once again lost her paladin companion and was disoriented when Valoku came to her rescue, taking her to his nether dragon lair. From Tyrygosa, he discovers the history of his kind's progenitor, Deathwing, and his relation to the Netherwing dragonflight. With the promise that Tyrygosa would free their brethren from their enthrallment, they partook in the battle for the Dark Portal against Ragnok Bloodreaver's forces.
Tyrygosa convinced Valoku and Zzeraku to battle their own people in an attempt to free the nether dragons from the control of Ragnok, who was leading an attack on the Dark Portal. He eventually placed himself in front of Tyrygosa to protect her from an attack by the enthralled nether dragons. His shield spell eventually faltered to their attacks, and he burned away.