Legendary Resistance (3/Day). If Subject 0-002 fails a saving throw, it can choose to succeed instead.

Captive Lure. Creatures that are within 60 feet Subject 0-002 and can see it's Lure, must make a Wisdom save at the start of their turn (DC 14).  On a failure, the creature is stunned until the start of their next turn.  To avoid making the save, Creatures may choose to avert their gaze, but to do so gives themselves the Blinded condition.

Stuck in it's Belly?.  If swallowed creatures deal at least 40 damage in one round, Subject 0-002 must make a DC 20 con save or regurgitate all creatures.  If the damage dealt is instead 80 or more, Subject 0-002 is forced to regurgitate all creatures.

Multiattack.  Subject 0-002 can make 2 bite attacks, or 1 Bite and 1 Swallow.

Bite. Melee Attack: +10 to hit, reach 10 ft., 1 target. Hit: 19 (2d10 + 8) piercing damage and 17(3d10) acid damage.   On a successful hit, the target must make a DC 23 strength save or be grappled by the creature. 

Swallow Strike. Must target a grappled creature.  +10 to hit,  1 target. Hit: 19 (2d12 + 8) piercing damage and 17(3d10) acid damage.   On a successful hit, the target is swallowed.  As long as the target remains inside the Gorm, they take 17(3d10) acid damage at the start of each of their turns.

Caustic Bile Spray. (Recharge 5 or 6)
As a bonus action,  Subject 0-002 sprays acid in a 45 ft cone.  All creatures in the area must make a Con save DC 19.  On a failure, Creatures take 10d8 acid damage, or half as much on a success.

Subject 0-002 has 4 legendary actions per round.  They must be used immediately after another creature's turn.

Grasping Arms (Costs 1 Action). The Target must make a DC 23 strength save.  on failure they are grappled by the creature.

Swallow Strike (Costs 2 Actions). Must target a grappled creature.  +10 to hit, reach 10 ft., 1 target. Hit: 19 (2d12 + 8) piercing damage and 17(3d10) acid damage.   On a successful hit, the target is swallowed.  As long as the target remains inside the Gorm, they take 17(3d10) acid damage at the start of each of their turns.

Recharge Spray (Costs 1 Action).  Auto recharge for Caustic Bile Spray in preparation for it's turn.  Doing this means no roll is needed to recharge the spray at the start of it's turn.