Albar Prentis

Prentis was a Tivolian who at some time died and was transformed into a ghost in the underwater base, the Drum, in 2119.

He killed commanding officer Jonathan Moran and transformed him into a ghost. He later did the same to crewmember Richard Pritchard. (TV: Under the Lake)

Behind the scenes
Prentis is unnamed in the episode. He is, however, named in the episode credits.