Regenerative Properties. For every 10 damage the Acid Worm Queen takes, it regains a d6 of lost health. If the roll is a 6, it summons 1 acid worm. The acid worm appears next to the queen. 

Legendary Resistance. If the Acid Worm Queen fails a save, it can choose to succeed instead. (3/day)

Summon Minion. The Acid Worm Queen summons d4 Acid Worms at points within 20 ft. that she can see. 

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: (2d6 + 6) [Piercing] damage. 

Acid Spray.  20 ft. Cone: DC15 save. Hit: (2d10+ 4) [acid] damage.

The Acid Worm Queen can use a bonus action to command any acid worms within 10 feet to attack a specific target. 

If the Acid Worm Queen takes more than 25 damage from a single melee hit, it can use a reaction to counter attack the attacker with its bite attack. If the bite hits, the original damage is halved. 

The Acid Worm Queen has 2 legendary actions, and gains them back at the start of its turn. 

Burrowing charge. (Costs 2 Actions). The Acid Worm Queen chooses a target within 60 ft. it can see and burrows into the ground. It can move up to double it’s movement speed, and when it gets to the target, makes a bite attack. 

Regenerative Frenzy. (Costs 2 Actions). The Acid Worm Queen heals d4 health and has resistance to non-magical damage until the start of its next turn.