William Abberton, or Nimrod, was the head of the Forge from its creation to its fall.
On 14 October 1914, Abberton was at the Forge, experimenting on humans with a vampire virus. The vampires overpowered their creator and escaped. Abberton was mortally wounded and took the drastic step of using the Twilight formula to save his life, becoming a vampire. (AUDIO: No Man's Land, Project: Twilight) Abberton took the codename Nimrod and, enhanced with cybernetics and specialised weaponry, sought to hunt the vampires down and destroy them. During this time he met the Sixth Doctor and Evelyn Smythe, who stopped him from killing the vampire Cassandra Schofield. (AUDIO: Project: Twilight)
Between 2002 and 2004, Nimrod headed Project Valhalla, trying to scavenge alien technology from a crashed alien spaceship in Lapland. The mission turned into a disaster and the area had to be sterilised when the ship turned out to be a prison for a world-killing, blood-formed entity known as Nyathoggoth. After Project Vahalla, Nimrod had Crichton, the Deputy Director of the Forge, assassinated so Nimrod could take it over. (PROSE: Project: Valhalla)
Nimrod encountered the Sixth Doctor again in late 2004, while aggressively acquiring a Huldran spacecraft, he also initiated Project Lazarus: an attempt to replicate his regenerations. Although the Doctor escaped, Nimrod had enough DNA information to create a clone of him; it was unable to regenerate, but had enough of the Doctor's attributes to be hired as a scientific advisor. When the Huldrans began attacking the Forge in retaliation, Nimrod had the clone brainwashed to believe he was the Doctor, had been stranded on Earth, and was assisting them to prevent the Huldrans destroying Earth.
By 2007, the constant Huldran attacks and the arrival of the Seventh Doctor caused several key Forge members to realise the truth of the clone's nature. While the Doctor solved the Huldran situation, the clone activated the Forge base's self destruct program. (AUDIO: Project: Lazarus)
In the 2020s, Nimrod remotely observed Iris Wildthyme's attack on a temporary Forge base in Weston-super-Mare. Iris talked directly into a camera to inform Nimrod of the damage she had caused to Oracle. (PROSE: Project: Wildthyme)
By 2025 he began using the name William Abberton again. Abberton tried to turn the Doctor's companion Hex against the Doctor by revealing the Doctor's involvement with the death of Hex's mother, Cassandra Schofield. After the Doctor initiated the self destruct of the Forge's beta base, Abberton was seemingly disintegrated by an alien device. (AUDIO: Project: Destiny)
However, Nimrod had managed to survive vaporisation, and, in a desiccated, near-dead state, had been connected to the main Forge computer, Oracle and was now the new leader of the Forge. The Doctor left a syringe containing the Twilight cure beside Nimrod, which would cure his vampirism. However, the vampire DNA was the only thing that kept Nimrod alive, and taking the Twilight cure would cause his death. Depending upon his decision, the fate of Nimrod and the Forge was unknown. (PROSE: Twilight's End)