Gila

Gila was a humanoid alligator. He was part of the mercenary gang known as the Four.

The Scarlet Empress sent Iris Wildthyme to bring her the Four, believing one of them had the jar containing Cassandra, the first Empress. In exchange she promised to cure the dying Wildthyme.

By the time the mission had been accomplished, Gila had reverted to being an alligator with no trace of humanity. After Cassandra had been freed, she killed the Empress, who had imprisoned her originally. Gila ate her corpse afterwards. (PROSE: The Scarlet Empress)

The Obverse Eighth Doctor had a large pet lizard named Gila who had spines and malevolent pink eyes. (PROSE: The Blue Angel)