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 root s . Though they grew haphazardly , they could later be grown in specific patterns and organisations . Many of these roots had black eye s . 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 telepathic ally communicating with other individuals , as well as physically and mentally modifying them . It could also grow tendril s 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 mutation s 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 wa 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 " )