Mirror Universe
This alien slave worked for the Tholians aboard the Federation starship USS Defiant under the Gorn slave master Slar in 2155.
When that ship was stolen from a Tholian dock and commandeered by Jonathan Archer, an unknown reptilian creature attacked and killed Kelby, one of Archer's officers. The alien slave worker was interrogated in the Defiant's briefing room as to the identity of the murderer. Eventually, he revealed that the killer was his slave master, Slar. (ENT: "In a Mirror, Darkly, Part II")