During the Voord invasion of the planet Hydra, Nebrin commanded an attack on the remains of the Hydran Navy which he considered the greatest threat to the Voord. The attack succeeded in sinking the Fortitude, the head ship of the flotilla, and a quarter of the other ships but Nebrin himself was knocked out and captured by Ian Chesterton. He remained a prisoner on the Vigilant for months until the flotilla reached the continent of Predora, where he was then freed by the Voord occupying Predora City.
He acted as Overlord Tarlak's right hand man when Tarlak arrived in Predora City and helped him command the Voord against the Hydran resistance led by the First Doctor. However, when Tarlak threatened to turn Susan into a Voord against her will to blackmail the Doctor, Nebrin had a change of heart and disrupted the ritual. Tarlak then subjected Nebrin to a mental onslaught, killing him. (AUDIO: Domain of the Voord)
Like all Voord, Nebrin was disciplined and coldly dismissive when it came to the realities of war. Nevertheless, he was surprised when Susan treated him with kindness during his imprisonment. The two of them spoke about their friends and family. Despite having not met them, Nebrin told Susan her grandfather was "a great man" and Barbara was "brave and kind." He gradually became more protective of Susan when Tarlak took her as a hostage. He tried to convince her to accept becoming a Voord for her own sake more than anything else, so that she would not otherwise be harmed or killed during the transformation ritual. Nebrin ultimate stopped the ritual and denounced Tarlak for going against Voord customs and saying the act was murder. With his dying words, he said that Tarlak had no honour. (AUDIO: Domain of the Voord)