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, 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. She eventually discovered the brain creatures and destroyed them, freeing the inhabitants of the city. (DW: The Keys of Marinus)
- The Morpho were not named on-screen, only in the script and credits. Their origins are unknown, but they claimed that their brains outgrew their bodies.