Crystalline Shell. The aatrilian serpent reflects all radiant damage it would take.

Camouflage. When the aatrilian serpent is still, it looks like an outcropping of crystals.

Firery Internals. All creatures the aatrilian serpent has swallowed, on their turn, take 4d8 fire damage.

 Magic Weapons. The aatrilian serpent’s weapon attacks are considered magical.

Swallow. The aatrilian serpent performs a bite attack on a target of medium or smaller size it has grappled. If it hits it swallows the target, ending the grapple, the target become restrained, blinded, and deafened, at the end of every other round the target takes 12d12 acid damage and if the target is reduced to -10 hit points they are disintegrated, and the target takes the bite damage.

Multiattack. The aatrilian serpent can perform three bite/swallow attacks, two lunging strikes, three headbutts, or two precise rends.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., 1 target. Hit: 3d10 + 10 piercing damage. 

Lunging Strike. Melee Weapon Attack: +4 to hit, reach 25 ft., 1 target. Hit: 4d10 + 10 piercing damage. The aatrilian serpent moves to up to 20ft even if it misses, if all potential areas are occupied, he attack instantly misses.

Headbutt. Melee Weapon Attack: +4 to hit, reach 5 ft., 1 target. Hit: 3d10 + 9 bludgeoning damage. 

Precise Rend. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 4d10 + 9 slashing damage, if it hits, it becomes a critical hit.