Ash Rat

Fire Heal. Fire and heat heal an ash rat's wounds. For every round that the creature is exposed to flame or heat intense enough to deal at least 1 point of damage, the creature instead gains 1 hit point of healing. Two or more ash rats touching each other provide enough heat for fire healing.

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.

Smoky Hide. An ash rat continually sheds smoke from its body. This smoky haze is so thick that the creature is permanently lightly obscured. Though it is difficult to see the ash rat because of the smoke rising from its body, the smoke itself is visible, provided that the area has sufficient light by which to see it.

Hot Body. Due to it's heated body, attempting to touch the ash rat deals 1 fire damage per round that a creature is in contact with the ash rat.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., 1 target. Hit: 2 (1d4 + 2) piercing damage. 

Flame Spit. Ranged Attack: +4 to hit, range 10 ft., 1 target. Hit: 2 (1d4) fire damage.