Spiritual Imp, from Ultima Underworld II
After the Avatar had finally managed to beat the challenge of the five colored pyramids in the Ethereal Void, still was lacking entrance to the shrine because of bars installed by the Guardian. However, the Imp hanging around gave some hints along with his mocking. After the Avatar had managed to enter the shrine, the Imp gloated the Avatar being now imprisoned like a rat.
He quickly lost his mocking tone when Altara's Scepter was used to cut off the Guardian's influence. The Imp didn't any longer want to speak with the Avatar, fearing to get punished by the Guardian for allowing this to happen.
The Imp also mocked that even the Time Lord wasn't able to escape from the Shrine while the Avatar was still inside.