Rock Creature

The Rock Creatures were large, orange, blobby creatures native to the Ogrons' home world. They preyed upon Ogrons, yet were worshiped fervently by them. The Ogrons were said to fear these "monsters" even more than they feared the Daleks.

During a human-Draconian expedition to the planet, the Third Doctor saw one of the creatures eat one of the Ogrons attacking them, causing the other Ogrons to run away. (TV: Frontier in Space)

The Rock Creatures were eaten by giant crabs who became the Ogrons' new gods. This amused the Overseer. (AUDIO: Planet of the Ogrons)

Behind the scenes
In the novelisation, the Ogron eater is a giant lizard that is said to bear a resemblance to a Tyrannosaurus rex.