Gwanzulum

The Gwanzulum were a shape-shifting species stranded on the planet Adeki.

Biology
In their natural form, the Gwanzulum were large, monstrous heads with muscular, stubby arms and legs.

The Gwanzulum were telepaths who could read their targets' minds and take the form of individuals from their memories. The gwanzulum were parasitic energy leeches, draining life force from and ultimately killing their targets.

History
The Gwanzulum were the oldest shape-shifting race, predating the Whifferdills and the Kymbra.

During a conflict known as the Shaper Wars, the Gwanzulum all but wiped out the Whifferdills. The wars ended with the last of the Gwanzulum stranded on the planet Adeki. They drained the life force of the Adeki natives, and remained alone on the planet.

The Seventh Doctor encountered the Gwanzulum when he stopped on Adeki for a fishing trip. Reading the Doctor's mind and beginning to feed off his life-force, the Gwanzulum took the forms of the Doctor's past companions and selves to trick him into letting them aboard the TARDIS. Horrified by carvings in a tunnel wall describing the Shaper Wars, and by an uncharacteristic suggestion by his "Fourth self" to violently wipe out the monsters, the Doctor saw through the Gwanzulums' deception and made his escape alone. (DWM: Planet of the Dead)

Behind the scenes

 * The Gwanzulum were an idea by John Freeman that Richard Starkings decided to use across almost every Marvel UK comic at the same time, Doctor Who Monthly included. Among their other notable appearances were the Combat Colin segments of The Transformers comics.