This strange Underdark moss is a useful ingredient in creating everburning torches and sunrods, because it’s highly flammable and burns bright and hot.
Effect: A creature in a square of ember moss takes 5 extra damage from fire attacks and a -4 penalty to saving throws against ongoing fire damage.
Usage: Ember moss is a good way for fire-based creatures to maximize their fire attacks. Place ember moss in a choke point with soldier or brute creatures blocking the path while artillery or controller creatures launch ranged fire attacks against the characters.
Published in Dungeon Master's Guide, page(s) 67.