Gotens (mirror symbiont)

Gotens was a Trill symbiont from the mirror universe, a symbiotic life-form that existed with humanoid Trill as a joined species. Its specific joining with the James host was unique, due to the fact that James was not from the mirror universe, but the primary universe. 

History
In 2375, the current host of the symbiont, Night, was killed in a console explosion aboard the when it was transported into the primary universe.

Lox has lured the Trill government into providing them with a suitable host named James. When James joined with the symbiont, he escaped the ship before it was destroyed. ("Pure Evil")

The symbiont provided James with an "evil" personality, and would be the force behind all of James' scheming. ("Secret Shuttles, Part II", "Mirrorlyness!")