Alpha Ankheg

Acidic Blood. Whenever the Alpha Ankheg is hit all creatures within 5ft of the Alpha Ankheg must make a Dexterity saving throw or they take 4(1d8) Acid Damage or half as much on a successful save (DC 13)

Multiattack. The Alpha Ankheg can make two attacks with its claws and one with its bite

Claw. Melee Weapon Attack: +5 to hit, reach 10ft., Hit: 7 (1d8+3) slashing damage. If a single target is hit by both claw attacks and is a Large or Smaller creature, it must make a Dexterity Saving throw or be knocked prone (escape DC 13)

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) slashing damage plus 3 (1d6) acid damage. If the target is a Large or smaller creature, it is grappled (escape DC 13). Until this grapple ends, the ankheg can bite only the grappled creature and has advantage on attack rolls to do so.

Acid Spray (Recharge 6). The Alpha Ankheg spits acid in a line that is 30 feet long and 5 feet wide, provided that it has no creature grappled. Each creature in that line must make a DC 13 Dexterity saving throw, taking 10 (3d6) acid damage on a failed save, or half as much damage on a successful one.

Acid Glob. If a hostile creature leaves its melee range the Alpha Ankheg can spit a sticky acidic glob at the creature. The target must make a Dexterity saving throw or take 4(1d8) acid damage and become restrained.

Acidic Eruption. When the Alpha Ankheg dies it explodes and sprays all adjacent creatures with acid. All creatures adjacent to the Alpha Ankheg must make a Dexterity saving throw or take 10(3d6) Acid Damage (DC 13)

Villainous Actions.

The Alpha Ankheg can only make one Villainous Action per round

Burrow. The Alpha Ankheg can burrow up to its burrow speed, this movement does not provoke Attacks of Opportunity

Taken Below!. The Alpha Ankheg can make an attempt to grapple and pull a target underneath ground

Acidic Sprinkler.  The Alpha Ankheg takes in a deep breath and squeezes out acid out of each of its wounds. All creatures within 30ft of the Alpha Ankheg must make a DC 13 Dexterity saving throw taking 10(3d6) Acid Damage or Half as much damage on a successful one.