Thordon

 was a "barbaric" planet, inhabited by the Thordonians and, allegedly among them, the Warlords.

It was visited by the Sixth Doctor and Peri Brown. There, they were given a phaser by the hands of a dying Warlord, a piece of technology not supposed to be on the planet due to its technology level; this led them to its very source, Thoros Beta. (TV: Mindwarp)