Masters of Karn

The Masters of Karn were the original native species of Karn, (AUDIO: Seven Keys to Doomsday) a planet in the constellation of Kasterborous, thus relatively close to Gallifrey. (TV: The Brain of Morbius) The Doctor described them as "the mightiest empire the galaxy had ever known". (AUDIO: Seven Keys to Doomsday)

History
Karn was originally a colony of the old Gallifreyan Empire in the days before Rassilon, (PROSE: Cat's Cradle: Time's Crucible) when the spacefaring Gallifreyans sought to spread their civilisation and knowledge to "lesser species" while setting themselves up as their gods. (PROSE: The Legacy of Gallifrey) This led to the Sisterhood of Karn, a remnant of the Pythias who once ruled Gallifrey, taking refuge on the planet after they were expelled by the triumvirate of Rassilon, Omega, and the Other. (PROSE: Cat's Cradle: Time's Crucible)

The Masters of Karn became interstellar conquerors in their own right, ruling hundreds of planets with the Citadel of Karn as their capital, until a civil war broke out among themselves at the peak of their power, culminating in an atomic catastrophe that collapsed their civilisation, leaving only primitive bands of brigands and farmers roaming what remained of the planet. At some point before their fall, the Masters created the Crystal of All Power, an extremely powerful device; fearing its power for destruction, they split it into seven parts, scattered across the planet.

Thousands of years later, the Daleks enslaved some of these survivors in their quest for the Crystal, but were driven off by an incarnation of the Doctor. (AUDIO: Seven Keys to Doomsday) The native population of Karn was eventually wiped out by the final clash of Morbius and Pandad's armies in the Time Lords' Civil War, leaving the Sisterhood as the only inhabitants of Karn (PROSE: The Legacy of Gallifrey) with the exceptions of Mehendri Solon (a surviving human member of the Cult of Morbius) and, for a time, of Morbius himself, in the form of his disembodied brain. (TV: The Brain of Morbius)