Kali Carash
Kali Carash was a being who could inhabit people's bodies. He crash-landed in South Africa, where he possessed a lieutenant and Tommy Watkins, and tricked the First Doctor into thinking he was dead.
He survived and possessed Jo Grant's friend Rody Fletcher using Tommy's army coat, and made the Third Doctor place it in the Vault.
Eventually, he was defeated by Ruth Matheson. This happened in the Vault when Charlie Sato wore the coat and possessed him. She used two of the artefacts in the vault. The first, a painting, was retrieved on a field mission involving the Fourth Doctor and Romana, which showed the manner of his death. The second, a crystal, containing some of Zoe Heriot's memories, was given to Brigadier Lethbridge-Stewart at the creation of UNIT. It was able to take minds from people. She took his mind from the coat and Charlie's body and smashed the crystal saving Charlie. (AUDIO: Tales from the Vault)
