Geravalon chameleon

Geravalon chameleons resembled Terran chameleons but were larger. They generally had green skin and their heads had human characteristics. Much like normal chameleons, they could change their skin colour to disappear into their surroundings. Absorption of DNA of other organisms could cause a chameleon to become a member of that species. (PROSE: Kiss of Life)

History
When one chameleon drank the blood of a human prince, Rodrique, she became a human called Sastra. She was mistaken for a slave girl by local man Padros, and later fell in love with Rodrique. When her body began to mutate, the Doctor realised that she was a chameleon native to the planet. To keep her alive, she would require a daily transference of human DNA, which Rodrique agreed to provide with a kiss. (PROSE: Kiss of Life)