Mentors had humanoid upper bodies and segmented tails. They had fins around their heads and large flaps between their arms and bodies. They came in a variety of skin-tones, including green and tan. They were cold-blooded and had both lungs and chest gills. Young Mentors also had poisonous stingers on their tails, but these were generally lost with age. (TV: Mindwarp) They required constant moisture to remain comfortable. (TV: Vengeance on Varos) Mentors were apparently quite long-lived; one individual lived for at least one hundred years. (TV: Vengeance on Varos, Mindwarp)