(coexisting on another dimensional plane)
Because he was a slave, the Kelpien did not actually have a name. However, in the mid-2250s Michael Burnham of the prime universe decided she was going to call him Saru, in honor of a respected friend. Later, the mirror Saru saved Burnham's life when Ash Tyler attempted to kill her.
Burnham later communicated with the primary universe Saru, who asked if there were any Kelpiens on board the Shenzhou. Burnham decided not to tell Saru about the existence of his mirror counterpart. (DIS: "The Wolf Inside")
Background information Edit
Like his primary counterpart, this version of Saru was played by actor Doug Jones.