Vengeance On Varos
The Mentors, also called Thoros-Betans, (Vengeance On Varos) were a race of amphibious capitalists from Thoros-Beta.
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. (Mindwarp) They required constant moisture to remain comfortable. (Vengeance On Varos) Mentors were apparently quite long-lived; one individual lived for at least one hundred years. (Vengeance on Varos, Mindwarp)
One Mentor previously became a member of the Crimson Hand. (The Crimson Hand)
During the early 23rd century, the Mentors were willing but suspicious traders with humans. (The Janus Conjunction)
A Mentor called Gom complained to the Psychic Paper Inc. First Technician called the Tenth Doctor in to deal with the complaint, who accidentally landed on the Mentor with his TARDIS. (Psychic Paper Inc Claims Department)
Mentors were a highly mercantile species, running such companies as the Galatron Mining Corporation and the Search Conv Corps.
They also kept slaves, transporting the Thoros Alphans from the neighbouring planet Thoros Alpha. The Mentors worshipped Morgo. They believed that the dead went to the Plague Hall of Mogdana. (Mindwarp)