AWWayofTime:lavaCrystal
This uses the player's life force to smelt stuff in a furnace.

Our smelting system is too basic for it to be possible even with addons. Will update the API to make it possible but I'm not going to add it natively

That's fair. Ideally, what was the criteria you wanted to use for fuel sources (besides "not coal")? It seems to me that other magical fuel sources, such as alumentum and (witchery) brews of combustion are pure fuel sources too.

No clue I didn't design it, I just rebalanced the mod and I don't really want to change Toops' design (unless he really never comes back).

I don't wish to add it natively because then it would be logical to also add support for botania/witchery (didn't know there was a brew of combustion, if that's a combustible item it can be added using minetweaker or hell even natively if you give me the name:metadata)/blood magic/ExU and that adds a ton of APIs that could potentially break.

An addon wouldn't be that hard to write though. I might if their API don't break too often.