Kro'ka

The Kro'ka was a being that controlled access between zones on the planet Bortresoye within the Divergent Universe. He referred to himself as an "Interzone Guardian". (AUDIO: The Creed of the Kromon)

The Kro'ka was tasked by the Divergence (and later Rassilon) to direct the Eighth Doctor and Charley Pollard through a series of zones, to observe their effects on the experiments therein. (AUDIO: Caerdroia)

Description
The Kro'ka was a shape-shifting creature of indeterminate size. Charley referred to him as "a little blobby weasel who does the Divergence's dirty work." At one point, he had two hands, though he did not normally have any. He did not have a neck or feet. (AUDIO: Caerdroia, The Next Life)

The Kro'ka conducted his work remotely using psychic powers, telepathically inspecting the thoughts and intentions of the people moving between zones. He was capable of casting sensory illusions, or removing sensory input as he saw fit. He was high-minded, but with the skills to back up his attitude. The Kro'ka was believed by the Doctor to serve his masters reluctantly and under duress. Despite their enmity, the Kro'ka expressed an admiration for the Doctor. (AUDIO: The Creed of the Kromon, Caerdroia)

Charley once described him as "a complete fraud and malicious piece of excrement in dire need of a damn good hiding." (AUDIO: The Next Life)