Elixir of Life

Elixir of Life is a product of the Sacred Flame, utilised by the Sisterhood of Karn to give them extended life.

It can also be used to heal even serious injuries. Time Lords occasionally used it when undergoing a difficult regeneration. (DW: The Brain of Morbius)

It is produced on Karn as water from underground springs pass through the rocks heated by the Sacred Flame directly below them. The rocks contain numerous rare minerals and compounds which are released into the water when heated. A goblet is placed below the flame to catch the Elixir.

It is most likely a key ingredient in Sisterhood Salve.

This may be a remnant of the Pythia's 'magic'.