The Tower in the Sky
The Mind Flayers were brought into the world by Azazel long ago. They disappeared when he did, but rumors have recently cropped up claiming they have been spotted.
Mind Flayers understand many languages, but are unable to speak vocally. They communicate telepathically using pictures and feelings.
They recently have been kidnapping villagers and taking their memories, although for what purpose is currently unknown. They attempted to take memories from Tristan Kroft, but were only partially successful as they were stopped before they could finish.