The Animus is an extraterrestrial life form created by the BBC for Doctor Who in 1965. It was later retconned into being a Great Old One during the period when Virgin Books tie-in novels related to Doctor Who were being published in the 1990s.
Background[]
The Animus is a Great Old One from the Lloigor race. It was the only one of its race to cross into the physical universe, establishing itself at Vortis and turning the formerly lush planet into an acidic wasteland. It manifested itself within the Carsenome, an organic self-healing palace. The Animus is capable of taking over anything living which came into contact with gold. It resembled a hybrid created by crossing a spider or plant with an octopus. It could generate a fungus-like sustenance which grew into Carsenome, its fortress. The Animus could also create webbing with which it ensnared its victims. It consumed organisms via direct mental adsorptions and its tentacles spread out like roots, absorbing matter and generating webbing.
Dividing the Animus resulted in fission, creating two Animus. If it was dying, the Animus would create a seed of itself, that would grow into a new Animus complete with the memories of the old one. A single tendril could regrow to an Animus. It generated a light which weakened or hypnotized individuals. The Animus communicated telepathically with its Zarbi slaves, siphoned water from the planet, and drew power from the planet itself. It was capable of creating force fields, could fly, projected gravity beams, and could draw other planets and moons toward Vortis. It created incredibly resilient four-armed webbed beings.
During the Last Great Time War, a conflict between the Time Lords and the Daleks, the Animus was destroyed, with its "carsenome walls crumbling".