Vissian

The Vissians were a humanoid civilisation notable for having three genders, which included male, female, and cogenitor. First contact was made by the NX-01 Enterprise in 2153.

Before In a Mirror, Darkly
In the mirror universe, a Vissian starship made contact with ISS Enterprise (NX-01). Although the contact initially went well, relations broke down after Captain Maximillian Forrest granted the resident cogenitor asylum. During the resulting battle, Starfleet captured the Vissians and the crew on board. Doctor Phlox and Chef conducted several experiments of the crew barring the cogenitor itself and tactical officer Veylo. The cogenitor was freed and sent to a Terran Empire starbase whilst Veylo was sent to Major Malcolm Reed's quarters so they could discuss an unspecified matter. Some Vissians were later eater or served as food by Chef. (Before In a Mirror, Darkly)