Big Boss Couatl

Innate Spellcasting. The couatl's spellcasting ability is Charisma (spell save DC 14). It can innately cast the following spells, requiring only verbal components:

At will: detect evil and good, detect magic, detect thoughts

3/day each: bless, create food and water, cure wounds, lesser restoration, protection from poison, sanctuary, shield

1/day each: dream, greater restoration, scrying

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.

Magical Resistance. The couatl has advantage on any magical effect saving throws targeting it.

Multiattack. The Couatl makes two attacks, one bite and one constrict. A bite can be exchanged for a tail attack.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one creature. Hit: 12 (2d6 + 5) piercing damage, and the target must succeed on a DC 14 Constitution saving throw or be poisoned for 24 hours. At the end of each of their turns afterwards, the target can reroll their Constitution saving throw. After resisting the poison, the target is immune to its effects for the next 24 hours.

Constrict. Melee Weapon Attack: +6 to hit, reach 10 ft., one large or smaller creature. Hit: 10 (2d8 + 3) bludgeoning damage, and the target is grappled (escape DC 15). Until this grapple ends, the target is restrained, and the couatl can't constrict another target.

Tail. Melee Weapon Attack:  +8 to hit, reach 10 ft., one Medium or smaller creature. Hit: 14 (2d8 + 5) bludgeoning damage, and the target must make strength saving throw (DC 14), on a failure the creature is flung backwards by 10 feet. If the target is a large creature or larger they succeed this saving throw.

Gaze of Madness (Recharge 6). The Couatl targets one creature it can see within 30 feet of it, it peers into the soul of that creature, filling its head with thoughts of fear and madness. The creature must make a wisdom saving throw (DC 15), on a failure the creature goes mad, falling to the ground prone and becomes paralyzed in fear, the creature must wait for another creature to use their action to help, on a success the target is brought back to their senses and is no longer paralyzed, at which point they instead get the effects of a success. On a success the target instead becomes frightened until the end of its next turn.

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 Couatl regains spent legendary actions at the start of its turn.

Tail. The Couatl makes one tail attack.

Detect. The Couatl takes the rolls for perception or casts detect thoughts.

Glare (Costs 3 Actions). The Couatl makes one Gaze of Madness attack (if it's charged).