Possession

Possession was the act of one being taking over the body and mind of another.

Examples of possession
Fenric possessed Doctor Judson and Captain Sorin, allowing him a direct hand in his revenge against the Seventh Doctor. (TV: The Curse of Fenric)

The Beast possessed Toby Zed, giving him the ability to breathe fire and survive in areas without oxygen. (TV: The Impossible Planet / The Satan Pit)

The Torajii sun possessed Hal Korwin and Dev Ashton, giving them the ability to vaporise a being by looking at them. (TV: 42)

The Isolus possessed Chloe Webber, giving her the ability to make drawings come to life and living things become drawings. (TV: Fear Her)

Cassandra O'Brien possessed Rose Tyler, when she decided she needed a new human body. (TV: New Earth)

The Bane possessed humans who consumed Bubble Shock!, turning them into zombies at their command. (TV: Invasion of the Bane)

The Family of Blood possessed 4 humans, giving the Family non-gaseous bodies to travel around in. (TV: Human Nature / The Family of Blood) The Gelth possessed dead humans, giving the Gelth bodies to use as 'vehicles'. (TV: The Unquiet Dead)

The Midnight entity possessed Sky Silvestry, giving her the ability to steal the voices of others. (TV: Midnight)

Death possessed Owen Harper after he was reanimated. (TV: Dead Man Walking)

The Psionovore Marchosias possessed Senator Waldo Pickering, giving him superhuman strength and allowing him to directly feed on others' fears. (AUDIO: Minuet in Hell)

The Pandora entity possessed Inquisitor Darkel's mind, killing her. She had previously occupied other host bodies, but she had always been driven out. (AUDIO: Gallifrey)