Volag-Noc

Volag-Noc was the coldest planet in the Mutter's Spiral and was the Human Empire's foremost prison world. It was run by robot Wardens and the android Governor Lok. The prison was taken over by Gurney and the real governor was locked up. After the Doctor had arrived, he had released Lok and Gurney was overthrown, yet killed on the surface by Baltazar.

Baltazar was imprisoned on Volag-Nok three times. Here he had first learned of the Infinite, and found the chip carriers were fellow prisoners Gurney and Captain Kaliko, and the messenger Ulysees Meregrass. (DW: The Infinite Quest)

The Doctor was sent there by the Shadow Proclamation along with a Sontaran, Ogron and a Draconian. (IDW: Fugitive)

Behind the Scenes
Volag-Noc is similar to the Klingon Prison Planet of Rura Penthe from the Star Trek franchise as both are extremely cold prison worlds.