Thain

The Thains were a peaceful humanoid race in the 30th century.

The Thains lived on a planet where they lived in peace, with no weapons. The exception was their museum, which stored relics from the 29th century, including a series of Heat guns.

At one point, Thain city was attacked by Kleptons, who kidnapped many Thains and planned to use the entire race as slave labor. The First Doctor, John and Gillian arrived on the planet shortly thereafter and helped the Thains repel the invaders and free their world. Their leader, Valda, thanked the three and invited them to stay on the planet, but they chose to return to their adventures in time and space. (COMIC: The Klepton Parasites)

By the 40th century, the Kleptons still hated the Thains, even though they had died out ten thousand years beforehand. (PROSE: Placebo Effect)

Other matters
Despite being from the far-future, specifically the 30th century, (COMIC: The Klepton Parasites) one source claimed that they had became extinct circa 6000 BC. (PROSE: Placebo Effect) Another source claimed that by 3999, the Thains had been extinct for 10,000 years, (PROSE: Placebo Effect) again contradicting their presence in the 30th century. (COMIC: The Klepton Parasites)