Mr Gibson was a shapeshifting robot.
Gibson blamed the Eighth Doctor for destroying his world. In fact, the Doctor freed the slaves he was keeping, as well as stopping his policy of throwing political opponents into a volcano under his palace. With the slaves rebelling, he panicked and dropped a nuclear bomb in the volcano, unintentionally killing his robotic mate and all his allies.
He later worked with Rum and Thélash to find Miranda Dawkins on 20th century Earth. He disguised himself as a Volkswagen to avoid drawing attention. The Doctor destroyed him by driving a car into him. (PROSE: Father Time)