Gruemaw Squirt (5e Creature)
From D&D Wiki
Small monstrosity, unaligned
Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 14 (5d4 + 2) slashing damage.
The immature form of the gruemaw. Capable of much more rapid movement and possessed of constant energy, most squirts wander away on their own for a short and violent life, maturing in exponential growth spurts every decade before reaching adult size within a century.