A unit with mossbody has a 75% chance to reduce incoming damage by 15 points, whenever it takes damage. This effect applies after protection as well as physical and elemental resistances. If -15 damage is insufficient to reduce the damage to zero, the moss "pops" into a cloud which affects 4 squares, inflicting 1 AN poison damage, and the spell effect is over.

Counterintuitively, mossbody can protect against elemental and armor negating damage, such as that from Mind Burn.