- You may be looking for another being known as the Veil.
The Veil were a reptilian species capable of taking over the bodies of other species.
The Veil were a reptilian humanoid race, with scaly skin and horns of various size protruding from their head and shoulders. They also had long tongues which they could flail and retract at will. The tongue would still appear when they possessed someone.
The Veil were capable of possessing other beings, effectively allowing them to "jump" into their bodies. When possessed, the Veil would be able to control the person and gain some of their memories, though the original person would be able to communicate with the Veil. (TV: Prisoner of the Judoon) This possession gave off a specific type of energy. Possession by a Veil would feel very unpleasant to the possessed victim, and the victim would also be able to feel the emotions of the Veil possessing them. (TV: The Vault of Secrets)
The Veil were an ancient species, conquering worlds long before Earth had formed. At some point before the 21st century, the Veil home planet was turned into a ball of ice when their star was extinguished, wiping out all but Androvax, who had been travelling the stars and returned to find his people dead. (TV: Prisoner of the Judoon)
Before they had died, a ship of 100 cryogenically frozen Veil were sent out into space, but crashed on Earth in the 1970s. It was taken and stored in a vault by the Alliance of Shades. After being sent to prison, Androvax found out about the ship and set out to save his people. He was fatally poisoned escaping from a Judoon prison and enlisted the help of Sarah Jane Smith and her gang to get to the ship. Androvax succeeded in reaching the ship, but sealed the vault and planned to engage the ship's engines within which would destroy the planet. With the help of Mister Dread, Androvax and the Veil ship were transmatted into space where they took off to find a new world to colonise and restore the Veil species. (TV: The Vault of Secrets)