Source: LotR book!verse
Disclaimer: Tolkien named these things and we owe everything to his imaginings.
Red and white flame... forged in heat beyond imagining by a cunning craftsman, made from the sinews of Arda’s dark places, hidden... secret... and oh so very ancient.
Carried across the water by the last of the Faithful... when others bowed the knee in homage to that dark overlord... this flame remained true. Not pure, never pure... how can something that transforms beating hearts to dead stones be pure?
‘It burns, it burns...’ said the Prince, before he too went to the waters, leaving behind this shattered inheritance.
Now the flame is changed – renewed, re-made, re-named... as is its master.