Inner Furnace - another lie our manuals have told?

[thejeff]

Just tested it without CBM. The MR check is definitely present and probably easy (+4). It does affect non-Abysian units and units that don't already have a heat aura.
Both Humanbred and regular militia got a heat aura. Summer Lions, who already have one, never increased it, but that may be due to high MR.

I have to say I'd like the spell a lot better if it didn't have the MR check and only affected either Abysians or units with heat auras. I don't think the heat aura boost is really that strong. Certainly not worth trying to spam a spell that costs gems.
And giving a heat aura to non fire resistant units is counterproductive.