In my 'enhanced state' it occurs to me that if I get hit by a fireball, or
walk through lava or somesuch nonesense that I would suffer from burns.
Revelation, eh? Well, if you've had burns then you know that cooling your boo
boo is better than heating it. But what do we do in bat? We build a
campfire.

So the idea is this...keep track of burns. when burned, a campfire wouldn't
give you as much +hp, but sitting in freshwater would help. Maybe the 'rain'
spell would have a healing effect on your burns.