Evolution's Champion

After becoming "the very culmination of natural selection" on its home planet by supplanting all other lifeforms and becoming the only living thing on the planet, the Greth claimed the title of Evolution's Champion. (PROSE: Out of the Box)

Behind the scenes
The title is reminiscent of Time's Champion, Life's Champion and Death's Champion, titles claimed at various times by the Doctor, the Master and the Meddling Monk. However, whether there was indeed an Eternal embodying Evolution who formally chose the Greth as her champion is not clarified in Out of the Box.