Phobian

The Phobians were the supposed inhabitants of Phobos, a moon of Mars. Stories described them as brownish-grey monsters with lots of arms and no faces. Kai Tobias noted that they made a strange screaming noise.

In actuality, the Phobians were construction droids which had originally been used to construct parts of the park and map the lunar terrain. Kai re-purposed and controlled the droids, using them to terrorise and attack the drennies living on Phobos. He needed to create a constant mix of fear and excitement among the park guests to appease the Entity of Fear, who fed on these emotions.

When the Eighth Doctor and Lucie Miller discovered what he was doing, Kai knocked them out and ordered Droid 4 to carry them up a mountain and throw them into a wormhole. The Doctor would later disable this droid by using his sonic screwdriver to unscrew components inside it. (AUDIO: Phobos)