Blisterbomb Rat

Keen Smell. The rat has advantage on Wisdom (Perception) checks that rely on smell.

Pack Tactics. The rat has advantage on an attack roll against a creature if at least one of the rat's allies is within 5 feet of the creature and the ally isn't incapacitated.

Blood Embers. When the rat takes damage of any kind except psychic or fire, each creature within 5 feet of it takes 2 (1d4) fire damage.

Blisterbomb. When the rat is reduced to zero hit points, it must make a DC 10 Constitution saving throw. On a successful save, the rat explodes, creating a 5-foot radius sphere dust cloud that obscures the area. On a failed save, the rat explodes, instead creating 5-foot radius sphere fireball. Each creature in that area must succeed a DC 11 Dexterity saving throw, taking 5 (2d4) fire damage and 5 (2d4) bludgeoning damage on a failed save, or half as much on a successful one.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) piercing damage.

Cinder Breath (Recharge 3–6). The rat exhales ash and cinders in a 15-foot cone. Each creature in that area must succeed a DC 11 Dexterity saving throw, taking 5 (2d4) fire damage on a failed save, or half as much on a successful one. When the rat successfully recharges this ability, it must make a DC 10 Constitution saving throw. On a failed save, it is reduced to zero hit points and automatically fails the saving throw from its Blisterbomb trait.