Intimidating Entry  Every opposing creature must make a DC 22 Wisdom save when the Abaia enters the battlefield. On a fail, they are frightened for up to 1 minute or until they succeed at a later saving throw. They may reattempt the saving throw at the end of their turn

Mucosal Epidermis  The Abaia cannot be grappled or restrained by physical means. It also gains advantage for saves against spells that cause grappled or restrained conditions

Legendary Resistance (3/Day)  If the Abaia fails a save, it can choose to succeed instead

Multiattack  The Abaia makes 2 tail attacks and one bite attack. The bite attack can be replaced with Swallow if grappling a creature

Bite   +17 to hit, 5ft, on target. Hit 28 (5d6 + 10) piercing damage. If the target is Large or smaller, the creature is grappled by the Abaia

Tail  +17 to hit, 45ft, one target. Hit 24 (4d6 + 10) bludgeoning damage. The creature must make a DC 20 Dex save, being grappled and restrained on fail

Swallow  If grappling a creature, the Abaia performs a bite attack against said creature. The attack hits and the target is swallowed. When swallowed, they are no longer grappled but are now restrained and blinded, and has total cover against any effects or attacks from outside the Abaia. At the start of the Abaia's turn, all swallowed creatures take 49 (14d6) acid damage

Lightning Surge  The Abaia releases a blast of electrical energy from it's body. All those within 60ft of the Abaia must make a DC 24 Dex save, taking 52 (8d12) lightning on a failed save, or half as much on a success

The Abaia can take 3 legendary actions. Only one legendary action option can be used at a time, and only at the end of another creature's turn. The Abaia regains spent legendary actions at the start of its turn.

Tail  The Abaia makes one tail attack

Move  The Abaia moves up to half its speed

Upchuck (Uses 3 Actions)  The Abaia spews forth the contents of it's stomach in a 60ft cone. Those within the cone must make a DC 22 Con save, taking 26 (4d12) acid damage on a fail and half as much on a success. All swallowed creatures are expelled from the Abaia and take 52 (8d12) acid damage.

Enter the description for how mythic actions work for your monster here.

Mythic Action Name (Costs # Actions). Enter the description for your mythic action.