Ancient Couatl

Innate Spellcasting. The couatl's spellcasting ability is Charisma (spell save DC 18). It can innately cast the following spells, requiring only verbal components:

At will: detect evil and good, detect magic, detect thoughts, command,bless, create food and water, cure wounds,

3/day each:  lesser restoration, Gust of Wind, sanctuary, shield, counterspell, wind wall

1/day each: heal, greater restoration, control winds, resurrection, plane shift

Magic Weapons. The couatl's weapon attacks are magical.

Shielded Mind. The couatl is immune to scrying and to any effect that would sense its emotions, read its thoughts, or detect its location.

Legendary Resistance (3/Day). If the couatl fails a saving throw, it can choose to succeed instead.

Bite. Melee Weapon Attack: +12 to hit, reach 5 ft., one creature. Hit: 8 (2d10 + 6) piercing damage, and the target must succeed on a DC 16 Constitution saving throw or be poisoned for 24 hours. Until this poison ends, the target is unconscious. Another creature can use an action to shake the target awake.

Breath Weapons (Recharge 5–6). The couatl uses one of the following breath weapons:

Radiant Breath. The couatl exhales radiant energy in an 90-foot cone. Each creature in that line must make a DC 21 Dexterity saving throw, taking 56 (16d6) radiant damage on a failed save, or half as much damage on a successful one.

Constrict. Melee Weapon Attack: +12 to hit, reach 10 ft., one Medium or smaller creature. Hit: 10 (3d8 + 6) bludgeoning damage, and the target is grappled (escape DC 18). Until this grapple ends, the target is restrained, and the couatl can't constrict another target.

Change Shape. The couatl magically polymorphs into a humanoid or beast that has a challenge rating equal to or less than its own, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the couatl's choice).

In a new form, the couatl retains its game statistics and ability to speak, but its AC, movement modes, Strength, Dexterity, and other actions are replaced by those of the new form, and it gains any statistics and capabilities (except class features, legendary actions, and lair actions) that the new form has but that it lacks. If the new form has a bite attack, the couatl can use its bite in that form.

Return to Celestia (1/Day). If the Couatl is reduced to less then a quarter of it's hit points, it will cast plane shift as a reaction.

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

Detect. The couatl makes a Wisdom (Perception) check.

Blinding Dust. Blinding dust and sand swirls magically around the creature. Each target within 5 feet of the creature must succeed on a DC 16 Constitution saving throw or be blinded until the end of the target’s next turn.

Wing Attack (Costs 2 Actions). The couatl beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 20 Dexterity saving throw or take 14 (2d6 + 7) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.