Oroborus
From Tardis Wiki, the free Doctor Who reference
An Oroborus was a serpentine non-Terrestrial, able to transverse dimensions and feed on time itself. It could take away chunks of the timeline; the more it took, the more it grew. It could shed its skin just like other snakes. Once it was fully grown it could consume an Earth-sized planet in hours. (K9TV: Oroborus)
