Morpho (species)

The Morpho were a race of disembodied brains with eyes on stalks. They created the city of Morphoton on Marinus and enslaved the populace to take care of them and do their will. They controlled them by using their mental powers to cast the illusion that the city was luxurious, when it was really filthy and squalid. They were so powerful that they could even enslave Time Lords. They enslaved Altos and Sabetha when they came to the city in search of the keys to the Conscience of Marinus. When the First Doctor, Susan Foreman, Ian Chesterton and Barbara Wright came to Morphoton, they enslaved them as well with the exception of Barbara, who awoke the next morning seeing the truth of her surroundings. The Morpho planned to force Ian and the Doctor into working parties, while Susan would take the place of Sabetha (required to serve the Morpho by illuding newcomers). Meanwhile, they planned to hunt down Barbara after her escape, but she discovered the Morpho and destroyed them, freeing the inhabitants of the city. (TV: The Keys of Marinus)

Behind the scenes
The Morpho were never named on-screen, their name being given only in the script and credits. Their origins are unknown, but they claimed that their brains outgrew their bodies.