Thain city

A city on an Earth-like planet was inhabited by Thains. In the 30th century it was attacked by Kleptons, who used their flying machines to abduct Thains and cause creepers to destroy many of their buildings. The First Doctor, John and Gillian arrived and helped the Thains repel the invaders. After following a Klepton to their underwater city, they returned to the Thains' city with the slaves they had freed. (COMIC: The Klepton Parasites)