Ankheg Stonejaw

Tunneler. The Ankheg Stonejaw can burrow through solid rock at half its burrowing speed and leaves a 15-foot diameter tunnel in its wake.

Bite. Melee Weapon Attack: +9 to hit, reach 15 ft., one target. Hit: 27 (4d10 + 6) slashing damage. If the target is a Huge or smaller creature, it is grappled (escape DC 16). Until this grapple ends, the Ankheg Stonejaw can bite only the grappled creature and has advantage on attack rolls to do so.

Petrification Breath (Recharge 6). The Ankheg Stonejaw exhales petrifying dust in a 30 foot cone and 5 feet wide, provided that it has no creature grappled. Each creature in that cone must make a DC 16 Constitution saving throw against being magically petrified. On a failed save, the creature begins to turn to stone and is restrained. The creature 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 until freed by the greater restoration spell or other magic.

Jaws of the Earth (Recharge 5-6). The Ankheg Stonejaw uses its mighty jaws to consume a 15-foot diameter sphere of rock and earth within 5 feet of it. It then regurgitates rock and debris in a 30-foot line that is 10-feet wide. Each creature in that line must make a DC 16 Dexterity saving throw to take half of (4d10) bludgeoning damage.