Caval was a Joebb.
When his people turned against the Klathi, Caval helped two of them, Danq and Yula, escape in one of their ships. They reached the vicinity of Earth during the Victorian period. A meteor storm caused them to crash on the planet.
When Caval turned against the Klathi due to their evil schemes, he instructed the robot Batella to act against the Klathi too. At the same time, the Klathi instructed Batella to kill Caval, the Seventh Doctor and all the other opposing threats, who Batella was originally programmed to protect. Confused with so many instructions, Batella self-destructed, taking the Klathi and their ship with it and saving London. (COMIC: Claws of the Klathi)