Ankheg Queen

Brute. A melee weapon deals one extra die of its damage when the Ankheg Queen hits with it (included in the attack).

Relentless (Recharges after a Short or Long Rest). If the Ankheg Queen takes 30 damage or less that would reduce it to 0 hit points, it is reduced to 1 hit point instead.

Multiattack. The Ankheg Queen can make three attacks, one with its bite and two with its claws.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 27 (2d10 + 10) Slashing damage plus 4 (1d8) Acid damage. If the target is a Large or smaller creature, it is grappled (escape DC 17). Until this grapple ends, the Ankheg Queen can bite only the grappled creature and has advantage on attack rolls to do so.

Claw. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 18 (2d8 + 8) Slashing damage plus 5 (1d8) Acid damage.

Acid Spray (Recharge 5-6). The Ankheg Queen spits acid in a line that is 60 feet long and 5 feet wide, provided that it has no creature grappled. Each creature in that line must make a DC 17 Dexterity saving throw, taking 54 (12d8) Acid damage on a failed save, or half as much damage on a successful one.