PROCESS

The Process is oviparous wormlike sentient annelid parasite looking much like a leech with lamprey-like mouths at each end. It moves by cartwheeling itself end over end, leaving a slime trail behind. It had clawed fins and red-brown skin which turned grey with age. It possesses some psychic powers and traps its victims in silk cocoon to  feed on their mental energy but also appears to be datavore, sustaining itself by consuming information.While originally not bigger than normal leeches, with enough food, it is able grow the several meters in lenght.
Its origin is unknown but one specimen is known to have been in Ealing, UK, during the 1990s, at which point it got on stow away in a time machine and disappeared from the planet.
Source: Doctor Who  universe, Cat's Cradle: Time's Crucible.