I remember there is a doctor who episode I think it was 1980s season. I think the master, or someone else, finds a volcanic vent that periodically emits a blue flame and/or gas that bestows eternal life. Who ever it was that entered it is too late or it changes back to the orange flame and they get incinerated. I don't recall the episode name but it exists.
shareThe Brain of Morbius.
"I'm not reckless . . . I'm skillful!"
What I described does resemble THE BRAIN OF MORBIUS but it was the 5th doctor and has THE MASTER in it and was from the 80s.
I found out the episode I was asking about was: PLANET OF FIRE
http://tardis.wikia.com/wiki/Planet_of_Fire_(TV_story)
The entire plot is re-telling of a film called SHE. (I think).
"The Master’s TARDIS materialises in a control room deep below the volcano. The “Master” enlists Peri’s assistance, on pain of death from his Tissue Compression Eliminator weapon, in controlling the machinery there to harness the power of Numismaton Gas, which is indeed a bright blue flame renowned for its healing properties. The Doctor takes advantage of the presence of the Numismaton flame to heal the ailing Malkon in the Cave of Fire.