Ovinnik

He lives in the drying barn where the grain is brought in over the fire, which is the most dangerous building on any farm, and he is the reason it usually does not burn. He looks like a large black dog made of soot, with eyes like coals, and he laughs, and the laugh is the worst part. Bring him the first sheaf and a cockerel at the turn of the year and the barn stands. Forget, and he will show you what he has been preventing.

Set the Barn: it does not attack creatures first. On its turn it fires the building, and the fire spreads a further 10 ft each round thereafter. Creatures caught in it take 1d8 fire per round, no save - it is a burning building, not an attack. Soot Maw: piercing, melee 5 ft, +3 to hit, 1d6+2, used only against those who stay to fight rather than fetch water.

Of the Drying Barn: within it he cannot be burned, blinded by smoke, or caught. Outside it he will not go. The Offering: a sheaf of grain and a bird set on the threshold ends the encounter and puts the fire out with it. A farm that pays every year never meets him at all, which is the whole arrangement.