Gwanzulum

The Gwanzulum were a species of shapeshifters 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. (COMIC: Planet of the Dead)

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

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. The "companions" attempt was wrecked by taking the form of Peri, who was not actually dead, and fighting among themselves in a panic to get him to take them. The "Doctors" instead worked together, with the Seventh missing uncharacteristic moments in the confusion.

Horrified by carvings in a tunnel wall describing the Shaper Wars, the Doctor attempted to warn his "other selves" that the Gwanzulum wanted to enter the TARDIS to spread to new worlds. However, an uncharacteristic suggestion by his "Fourth self" to violently wipe out the monsters caused him to see through the Gwanzulum's deception and made his escape alone. (COMIC: Planet of the Dead)

Behind the scenes
The Gwanzulum were created by John Freeman and Lee Sullivan for the Doctor Who Magazine comic story Planet of the Dead. Due to the comic being an anniversary issue the Gwanzulum's shapeshifting abilities were used as an excuse to include various past Doctors and companions. Editor Richard Starkings decided to use the Gwanzulum across multiple Marvel titles to see if readers noticed their "secret invasion". This decision meant that while they were created as Doctor Who aliens the Gwanzulum actually made their first appearance in Lew Stringer's Combat Colin as part of. Other notable appearances were in the and  periodicals.