It first appeared on one of rim worlds of a galaxy with over twenty inhabited planets. It contaminated the planet's water sources and then began grabbing people and absorbing their blood. After drinking the blood of every living thing on a planet it would travel to another planet with life. After killing billions of people, the Nyathoggoth was weakened and cornered on a backwater planet. It could not be killed, so it was put in a prison ship that was programmed to fly into a black hole. The navigation systems of the ship failed and it crashed in the Laplands in the early 2000s.
The Forge sent a retrieval team led by Nimrod to collect the technology from the ship, calling the operation Project: Valhalla. The Nyathoggoth tricked Nimrod into deactivating the force field containing it. Cassie Schofield allowed it to feed on her, infecting it with the Twilight virus, which weakened the creature. Nimrod managed to interface with the ship's computer and activate its self-destruct protocols, and turn the force field back on to contain the explosion.
The Nyathoggoth took control of Cassie and had her fight Nimrod, but threw off the influence long enough to stab herself instead of him. Communicating through her, the Nyathoggoth said it would give Nimrod great power if they worked together, but Nimrod would not accept. The ship was destroyed, and the Nyathoggoth along with it.