Firekin/Flamekin are an NPC-only protected race in the Deadlands. They are members of the other mortal races (Humans, Elves, etc) who have been infused with a heavy dose of Flame energy. They are particularly prevalent in Deadlands because of a treaty made between the mortal plane and the Plane of Flame several years ago. CJ, Firekin are referenced on page 14 of the Deadlands Player's Guide; two prominent Human Firekin NPCs are Paladin Ember Brunswick (played by Stacey) and Justicar Julia Tavistock (played by myself).
It is not possible to play a PC Flamekin. It is, however, possible to be "touched" by any of the eight prime Elements and receive minor abilities. This process must be carried out via IG roleplay and is subject to Plot approval.