M is for... Maren

Maren was the ancient leader of the Sisterhood of Karn. This group worshipped the Sacred Flame, which rose up through a fissure from deep underground in their cavern temple. It heated the surrounding rock, producing a strange liquid with remarkable powers. Known as the Elixir of Life, it could prolong a person's lifespan indefinitely, and also had great healing powers.

Maren was an old woman when she first began to take the Elixir as a member of the Sisterhood.

The planet Karn lay in the same region of space as the Time Lord world of Gallifrey. The Sisterhood had once been close allies of the Time Lords, allowing them use of the Elixir to assist with regeneration problems. 

Then, the power-mad President of the High Council of Time Lords - Morbius - led an army of followers on a rampage through space towards Karn, having promised them access to the Elixir. Morbius was defeated there, and Maren was present at his execution.

The Sisterhood withdrew to their temple after this, destroying any spacecraft which came close to Karn and paranoid that the Time Lords might take the Elixir for themselves.

The Doctor's TARDIS was redirected to Karn by his people when they learned that part of Morbius had survived - his living brain. Maren assumed he was there to steal the Elixir, which was running out as the Flame was dying. He was able to restore it, and Maren eventually accepted that Solon - a surgeon who lived on Karn - had somehow managed to save the Morbius' brain. He was building a monstrous new body for it.

After Morbius and Solon had been defeated, the Doctor was left close to death. Maren accepted the Doctor's argument that even the Sisterhood needed change and evolution, otherwise there was no progress. Knowing that her deputy, Ohica, would make a fine leader, Maren sacrificed herself by giving the Doctor the last of the Elixir.

Everyone saw her revert to her youthful form before vanishing.

Played by: Cynthia Grenville. Appearances: The Brain of Morbius (1976).

• The Sisterhood are unable to detect the mind of Morbius because Time Lords know how to shield themselves. But why can't they see into Solon's mind - or Condo's?