The Volcanic Efreet has the “In Flames” ability, which says “Your creatures recover health from Burn instead of taking damage. Creature starts battle with Burn for 5 turns.” But this only seems to work if it’s already injured. If the efreet is at full health, it takes damage from burn at the beginning of its turn.
(This is reproducible every time, as far as I can tell, and it didn’t have Blight or anything. It heals correctly as long as it’s injured.)
iOS Siralim 2.0.9.