Memeovore

The Memeovore, also known as the Fendahl Predator, was a life form from the Fifth Planet that evolved to feed on the Fendahl. The Memeovore examines and destroys probabilities, consuming the energy thus released- it feeds on concept and meaning itself.

The Memeovore was trapped on the time-looped Fifth Planet, but was released by the renegade Celestis One, which (as he hoped) attacked his homeland of Mictlan. The Eighth Doctor saved the universe by commanding a fleet of TARDISes to sever Mictlan's ties to the rest of the universe, setting it and the Memeovore adrift in an interdimensional void.