Place of origin:
Actron Pleiades system
Described by The Doctor as a particularly nasty example of extraterrestial life, the Vurosis are intelligent proto-molecular parasites from the Acrtron Pleiades star system, preying on defenceless planets with easily adaptable carbon-based life forms such as Earth. Arriving as seeds, the Vurosis subsequently germinate underground that spread and reproduce by transforming the indigenous species into others like itself using a process described as telekinetic transmutagenics, resulting in the victims being mutated into Vurosis-like entities on the cellular level.
When The Doctor encountered a Vurosis, it was trapped at the bottom of an old well in the village of Creighton Mere, having become separated from its brain – which physically manifested as a green stone – during the crash and thus reduced to operating on instinct as it grew and developed within the well. Fortunately for the Vurosis, its brain had been discovered some years back, eventually falling into the hands of student Nigel Carson, telepathically prompting him to dig to under the well with promises of wealth and power (There was a story about a highwayman who had lost his loot at the bottom of the well). Encouraging two of his friends to dig with him, they made significant advances towards the well, although they were also aided by the fact that the local lord, Henry Gaskin, still had access to an old tunnel that his father had dug some years back which they could use as a starting point.
Arriving in the village for a holiday, The Tenth Doctor and Martha Jones learned the story of the highwayman and the well from local tramp Old Barney, only to be shocked when Barney was disintegrated directly in front of them; the Vurosis brain had attempted to transform Barney to act as a new body for it, but the fragility of the human form had rendered such an action impossible. Investigating the well as Nigel continued to dig the tunnel, The Doctor was pulled into the well by the Vurosis’ body – operating on instinct to attack the ‘intruder’ – leaving Martha to travel down the Gaskin Tunnel just in time to discover that one of the students was mutating into a monster after coming in contact with the highwayman’s skeleton.
As the mutated student attacked Martha, The Doctor broke through the crumbling wall that connected the tunnel to the well, using the sonic screwdriver to drive the creature off as he and Martha escaped. Although recognising the creature as a mindless Vurosis that had mutated the students on instinct, The Doctor was unable to stop the student from uniting the brain and the body, but the Vurosis’s current lack of energy limited the danger it posed at present; it had to spend its time immediately after ‘waking up’ establishing defences rather than killing anyone. Provoking the Vurosis into attacking him before it was fully charged, The Doctor drew on the mental energy of Martha and their current allies from the village, turning the Vurosis’s attack back on itself and causing its entire form – body, brain and all – to crumple into dust.