Vurosis

The Vurosis was a type of parasitic lifeform.

Biology
Despite its appearance, the Vurosis was neither a plant or an animal, unlike any Earth life and immune to any Earth-based toxin. The Vurosis' main body was composed of a system of interlocking white roots. Though they grew haphazardly, they could later be grown in specific patterns and organisations. Many of these roots had black eyes. These roots were warm to the touch and glowed green in the dark.

The Vurosis' brain was a small, stone-like structure, about the size of a human heart. It could be separated from the main body, but the intelligence of the Vurosis would decrease. The brain was capable of telepathically communicating with other individuals, as well as physically and mentally modifying them. It could also grow tendrils to manipulate its environment. The brain would give off radiation that would eventually become fatal.

The Vurosis could telepathically modify other carbon-based life. When modified, the individual would grow tendrils throughout their body and would take on the bioluminescent glow of the Vurosis. These modified individuals would be loyal to the Vurosis and would do its bidding while it was stuck underground. The mutations could also be overloaded, killing the individual and turning it to dust. In individuals who survived the modification process, the mutation was reversible by the Vurosis releasing its telepathic hold over them. (PROSE: Wishing Well)

Life cycle
The Vurosis began life as a seed, which set root on a planet with carbon-based life. The Vurosis grew underground for hundreds of years, spreading its tendrils throughout the area.

The Vurosis eventually reached maturity in a process called The Rising. This occurred when the brain was brought to the main body. The brain would attempt to bring itself closer to the body of the Vurosis, modifying the minds of people around it to further their objectives. Until the brain was reunited, both the brain and the body had limited abilities, with the body doing little more than reacting to its environment.

Once the Vurosis obtained its brain, it reached its final stage of development. The main body formed into a massive, worm-like structure and brought itself to the surface. The tendrils underground spread and engulfed any living creatures for energy. At this stage, it was still weak, needing all its energy to grow. Eventually, it would have enough energy to spread its roots out further, reproducing as it went. At that point, it was nearly impossible to kill, as any remaining sections were able to regrow the whole body. (PROSE: Wishing Well)

History
At some point, a Vurosis was brought to the wishing well in Creighton Mere. It grew for hundreds of years, filling the well and becoming interlaced with the nearby soil.

In 1902, Rupert Gaskin started construction on the Gaskin Tunnel, believing that there was treasure at the bottom of the well. Though he reached nearly to the body of the Vurosis, he died from influenza and the construction was stopped. In 1943, Nigel Carson's grandfather found the tunnel and explored it further. He was able to find the brain, and took it. Though he wanted to go back and find this "treasure", he eventually succumbed to the brain's radiation. Eventually, the brain was passed on to Nigel Carson, who was able to get together a team to dig. They finally broke through and the Vurosis took over Duncan Goode. Using Duncan's body, it hunted down Nigel and tried to take back the brain. After conflicts with the Doctor, the Vurosis took the brain back to the well. Though the Vurosis was awakened, the Tenth Doctor was able to force its mutagenic powers back on it, killing it. (PROSE: Wishing Well)