Karn

Once a colony of Gallifrey, Karn later served as the home of the powerful Sisterhood of Karn and bolt-hole of the Time Lord criminal Morbius.

Characteristics
During Morbius's attempted re-birth, Karn had become a burned-out and exhausted planet; a barren and rocky wasteland with many ruins and abandoned industrial plantations. It was also littered with the wreckage of crashed spaceships bought down by the Sisterhood out of fear of thief of the Elixir of Life. (DW: ''The Brain of Morbius


 * By implication, Karn resided near Gallifrey, as well as having a known importance place in the history of Gallifrey and of the Time Lords.

Early History
Karn was originally a colony of the old Gallifreyan Empire which existed in the days before Rassilon. The Sisterhood of Karn were a remnant of the Pythias who once ruled Gallifrey before being expelled by the triumvirate of Rassilon, Omega, and the Other. (NA: Cat's Cradle: Time's Crucible

Modern History
In the Rassilon Era, the Sisterhood guarded the Sacred Flame. The Sacred Flame was used to distil the Elixir of Life, which can aid a Time Lord who is experiencing difficulty with regeneration. (DW: The Brain of Morbius) In the far future, Morbius, a renegade Time Lord, in his bid for galactic conquest, came to Karn with a mercenary army promised the Elixir of Life. The Time Lords cornered him there defeating him, trying and executing him. But before his death, Solon, a member of the Cult of Morbius, removed his brain and preserved it vowing to resurrect him at a later time. Solon settled on the planet in a disused Hydrogen plant researching a way to make Morbius live again, and using body parts from dead crew members of crashed ships to create a new body for him.

Apocryphal Information
The Crystal of All Power, sought by the Doctor and the Daleks, resided on Karn. (SP: The Seven Keys to Doomsday)

Behind the Scenes
Karn originated in a theatrical play, The Seven Keys to Doomsday, written by Terrance Dicks, who later re-used the name when writing the script for The Brain of Morbius. The play featured a non-canonical Doctor played by Trevor Martin. The presence of this other Fourth Doctor would make the play difficult to integrate into known continuity. The Doctor does not make reference to these earlier events on Karn in any other story.