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.

Chameleon Skin. The yuan-ti has advantage on Dexterity (Stealth) checks made to hide.

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), cause fear, entangle

3/day each: darkness, dispel magic, protection from energy (self only), suggestion

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

Malison Type. The yuan-ti has a Human body with snake head and serpentine lower body instead of legs.

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

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 6 (1d4 + 4) piercing damage plus 7 (2d6) poison damage.

Constrict. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage, and the target is grappled (escape DC 15). 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: +7 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) slashing damage.

Longbow (Yuan-ti Form Only). Ranged Weapon Attack: +4 to hit, range 150/600 ft., one target. Hit: 5 (1d8 + 1) piercing damage plus 7 (2d6) poison damage.

Polymorph into Snake (Recharge 6). The yuan-ti targets a creature it can see within 60 feet of it. The target must succeed on a DC 14 Wisdom saving throw or be transformed into a Tiny poisonous snake, as if affected by the polymorph spell.