Kago-Darr's species had a larger than average head, with mainly white hair, and some red and blue marking along the top. A ridge went down the center bald-spots of their heads, and there was a ridge-face on the sides of their eyes.
In early 2152, a member of this species was found in an automated repair station, basically dead; the computer had been using his brain to run its systems. He'd been there for several years. (ENT: "Dead Stop")
In early 2153, Kago-Darr, a bounty hunter that competed with Skalaar, tried to take Captain Jonathan Archer from him to hand to the Klingons. But they outmaneuvered him, and disabled his vessel. Later while repairing it, Enterprise contacted him for information on Skalaar's whereabouts, but all he knew was that he was probably half way to the Klingon border by then. (ENT: "Bounty")