Fendahl Predator

The Fendahl Predator was a creature that evolved on the time accelerated Fifth Planet to feed on the Fendahl themselves.

They were a living absence which insinuates itself into subatomic quantum interactions thus collapsing the alternate probabilities by the act of its observation and feeds upon the energies that are released. This makes them Memevores, creatures that devouted concept itself and reach were capable of encompassing all of time and space.

A faction of Time Lords used a herd of TARDIS's to break the time barrier around the Fifth Planet in order to free the Fendahl Predator for use against The Enemy. (BBC: The Taking of Planet 5)