Mindbending

Mindbending was a form of psychic wrestling played by Time Lords. Usually it was only a game, but it could end in deathlock. The competitors placed their heads against the mindbending device and the process began. It involved mental warfare hence, mindbending. The Fourth Doctor and Morbius entered a mindbending contest on the planet Karn. The Doctor won, though nearly at the cost of his own life. (DW: The Brain of Morbius)

Behind the scenes
During the mindbending sequence several faces are shown, they were images of the production team. The appearances of these images has lead to several theories concerning the Doctor's past regenerations. One such theory revolves around the character of The Other, whom the Doctor is suggested to be related to, for more information see article on The Other.