Bolstering Presence. The yuan-ti magically emanates life-giving energy within 30 feet of itself. Any ally of the yuan-ti that starts its turn there regains 5 (1d10) hit points.

Shapechanger. The yuan-ti can use its action to polymorph into a Medium snake, or back into its true form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn’t transformed. It doesn’t change form if it dies.

Innate Spellcasting (Yuan-ti Form Only). The yuan-ti’s innate spellcasting ability is Charisma (spell save DC 14). The yuan-ti can innately cast the following spells, requiring no material components:

At will: animal friendship (snakes only)

3/day: suggestion

Magic Resistance. The yuan-ti has advantage on saving throws against spells and other magical effects.

Spellcasting (Yuan-ti Form Only). The yuan-ti is a 16th-level Simic spellcaster. Its spellcasting ability is Intelligence (spell save DC 15, +7 to hit with spell attacks). The yuan-ti has the following wizard spells prepared:

Cantrips (at will): acid splash, light, mending, poison spray, shocking grasp

1st level (4 slots): detect magic, grease, shield

2nd level (3 slots): alter self, blindness/deafness, enlarge/reduce, hold person

3rd level (3 slots): counterspell, dispel magic, haste, protection from energy

4th level (3 slots): confusion, conjure minor elementals, polymorph

5th level (2 slots): cone of cold, creation, hold monster

6th level (1 slot): move earth, wall of ice

7th level (1 slot): prismatic spray

8th level (1 slot): control weather

Multiattack (Yuan-ti Form Only). The yuan-ti makes two ranged attacks or three melee attacks, but can use its bite and constrict attacks only once each.

Bite (Snake Form Only). Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 6 (1d6 + 3) piercing damage plus 10 (3d6) poison damage.

Constrict. Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 10 (2d6 + 3) bludgeoning damage, and the target is grappled (escape DC 14). Until this grapple ends, the target is restrained, and the yuan-ti can’t constrict another target.

Scimitar (Yuan-ti Form Only). Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) slashing damage.

Longbow (Yuan-ti Form Only). Ranged Weapon Attack: +6 to hit, range 150/600 ft., one target. Hit: 12 (2d8 + 3) piercing damage plus 10 (3d6) poison damage.

Call Reinforcements (1/Day). The yuan-ti magically calls 2d4 yuan-ti malisons or category 1 krasis. While outdoors, the yuan-ti can call 1d4 category 2 krasis instead. The called creatures arrive in 1d4 rounds, acting as allies of the yuan-ti and obeying its spoken commands. The creatures remain for 1 hour, until the yuan-ti dies, or until the yuan-ti dismisses them as a bonus action.