Baby Stonemaw

False Appearance. While the stonemaw remains motionless in Ball Form it remains indistinguishable from a normal boulder.

Tunneler. The stonemaw can burrow through solid rock at half its burrowing speed and leaves a 10 foot-wide, 10-foot-high tunnel in its wake.

Multiattack. The stonemaw makes one Bite attack and two Slash attacks.

Slash. Melee unarmed Attack: +8 to hit, reach 5 ft., one target. Hit: 8 (1d6 + 5) slashing damage.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 18 (3d8 + 5) piercing damage. On a hit, the target must make a DC 12 Constitution saving throw. On a failed save, the creature magically begins to turn to stone and is restrained. It must repeat the saving throw at the end of its next turn. On a success, the effect ends. On a failure, the creature is petrified, but still aware of its surroundings, for 1 minute or until freed by the greater restoration spell or other magic.

Rolling Charge. Recharge. (Recharge 4–6). The stonemaw charges 40 feet. Any creature caught in this path is pushed forward with it and must succeed on a DC 16 Strength saving throw or take 7 (2d6) bludgeoning damage, or half as much on successful save. Additionally a creature that fails the save is knocked prone. If the stonemaw pushes the creature into a wall the damage is 24 (7d6) instead.

Ball Form. The stonemaw withdraws into a ball. Until they emerge, they gain a +6 bonus to AC. While in the shell the stonemaw  speed is 0 and can't increase and the only actions you can take are Rolling Charge and a bonus action to emerge from your shell.