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 Charlotte Pollard through a series of zones, to observe their effects on the experiments therein.

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." (AUDIO: Caerdroia) At one point, he had two hands (not normally having any). (AUDIO: 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. (AUDIO: The Creed of the Kromon)