Valerus was a world in a sub-atomic universe and the home of the Valerons. The Third Doctor and Liz Shaw used a sub-space radio to transport themselves to Valerus, where they were captured by the Valerons and escaped with the aid of Dynil. They were abruptly brought back to the Doctor's lab when the Brigadier, unaware of the adventure they were having, shut off the sub-space radio. Valerus was presumably destroyed by the radiation from the blue star some time afterwards. (PROSE: A Universe Called Fred)