Fire Dancer Swarm

Fire Form. A creature that touches the swarm or hits it with a melee attack while within 5 feet of it takes 5 (1d10) fire damage. In addition, the first time the swarm enters a creature's space on a turn, that creature takes 5 (1d10) fire damage and catches fire; until someone uses an action to douse the fire, the creature takes 5 (1d10) fire damage at the start of each of its turns.

Illumination. The swarm sheds bright light in a 30-foot radius and dim light to an additional 30 feet.

Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Tiny creature. The swarm can't regain hit points or gain temporary hit points.

Water Susceptibility. For every 5 feet the swarm moves in water, or for every gallon of water splashed on it, it takes 1 cold damage.

Swarm. Melee Weapon Attack: +8 to hit, reach 0 ft., one target in the swarm's space. Hit: 21 (6d6) fire damage, or 10 (3d6) fire damage if the swarm has half or fewer hit points.