Keen Smell The swarm has advantage on Wisdom(Perception) checks that rely on smell.
Swarm The swarm can occupy another creatures space and vice versa, and the swarm can move through any opening large enough for a tiny rat. The swarm cannot regain hit points or gain temporary hit points.
Flame Feast The swarm regains hitpoints equal to half of any fire damage it would have received before its immunity. The Swarm must also use its entire movement to move towards and large source of open flame.
Fiery Fur The swarm ignites any flammable objects that are not worn or carried, located within its space at the beginning of its turn.
Bite (greater than half HP) Melee Weapon Attack: +2 to hit, reach 0 ft., one target in the swarms space. Hit: (2d6) piercing damage + (2d4) Fire damage.
Bite(Less than half HP) Melee Weapon Attack: +2 to hit, reach
0 ft., one target in the swarms space. Hit: (1d6) piercing damage + (1d4) fire damage.