The Brains of Morphoton were once the masters of the city of Morphoton on Marinus, but their brains outgrew their bodies and had to be encased in protective glass domes. They look like brains with a pair of eyes on stalks, and a heartbeat sound echoes around the room in which they live. Their intelligence created the entire city of Morphoton, and they have found ways to maintain their control.
When a visitor arrives in Morphoton, he is subjected to an initial blast of light that temporarily makes him see Morphoton as the Brains wish. Instead of dirty rags, the visitor sees gowns; filthy mugs become crystal goblets or advanced scientific instruments. Through this form of deep hypnosis, the visitor to Morphoton believes that he is granted his every desire. The initial blast also seems to induce drowsiness, and once the visitor has gone to sleep, a servant will enter and place a sumnar disc on his forehead, causing him to sleep and forget life before Morphoton. A device called the Mesmeron is activated once the sumnar disc is in place; through a combination of light and a loud klaxon, it more permanently imprints the brain to see the false Morphoton. This leaves a mild irritation on the forehead, but aside from that, the visitor has become completely convinced that Morphoton is a luxurious resort...and he has also gone completely under the control of the Brains of Morphoton. However, once someone has seen the truth about Morphoton, their memory cannot be erased and the Brains are forced to destroy them.
The Brains need humans to feed them and carry out their orders, using them like slaves or machines. These humans may be sent to various working parties, in the haulage gangs or solving the problem of how to increase manpower, or trained as servants. The Brains of Morphoton readily kill anyone who fails them.
When the TARDIS crew arrived in Morphoton, all fell under the Brains' spell except for Barbara, who managed to smash their equipment and some of their glass cases. The Brains were killed, their eyestalks collapsing, and the entire population of Morphoton was released from their hypnotic trance. The city was burned by the angry populace.
