Xyris, Apex of the Skies.

Legendary Resistance (3/Day): If Xyris, Apex of the skies fails a saving throw, it can choose to succeed instead.

Snake Summoning. On every successful hit, Xyris Summon's 1d4 Giants Poisonous snakes on every third successful hit in a row Xyris summons 1d4 giant Constrictor snakes and on every ten successful hits in a row, Xyris summon 1 Titanoboa. The snakes die when Xyris does.

Gift of flight. All snakes summoned by Xyris have a flight speed equal to Xyris's Flight speed.

Apex Status. Due to Xyris's title as an Apex of Ikoria, Most normal creatures will not fight it more likely choosing to Flee or leave it alone. The main exception to this are players, NPC's above level 13 and other Apex Creatures.

Regurgitation. If Xyris takes 40 damage in a turn he regurgitates up any swallowed creature on a failed DC 20 con save.

Multiattack. Xyris can make 2 bite attacks and a slam attack each turn

Bite. Melee Weapon Attack: +17 to hit, reach 5 ft., 1 target. Hit: 14 (3d8 + 9) piercing. damage. 

Slam. Melee Weapon Attack: +17 to hit, reach 10 ft., 1+ target. Hit: 11 (3d6 + 9) Bludgeoning damage. 

Swallow. If Xyris hits a creature with two bite attacks in the same action it can attempt to swallow the creature if it is of huge size or smaller, The creature being swallowed must make a DC 19 Dexterity check or be swallowed taking 8d6 acid damage on the beginning of each of its turn The swallowed creature is restrained.

Summon snake (Costs 3 Actions). Once below half HP Xyris can choose to activate its snake summoning trait picking any of the possible options.

Detect. (Costs 2 actions) Xyris makes a perception check