Armor Class 12
Hit Points 66 (12d8 + 12)
Speed 30 ft.
Skills Deception +5, Stealth +4
Damage Immunities poison
Condition Immunities poisoned
Senses darkvision 60 ft., passive Perception 11
Languages Abyssal, Common, Draconic
Challenge 3
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.
Magic Resistance. The yuan-ti has advantage on saving throws against spells and other magical effects.
Malison Type. The yuan-ti has one of the following types:
Multiattack (Yuan-ti Form Only). The yuan-ti makes two ranged attacks or two melee attacks, but can constrict only once.
Bite (Snake Form Only). Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: 5 (1d4 + 3) piercing damage plus 7 (2d6) poison damage.
Constrict. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) bludgeoning damage, and the target is grappled (escape DC 13). 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: +5 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) slashing damage.
Longbow (Yuan-ti Form Only). Ranged Weapon Attack: +4 to hit, range 150/600 ft., one target. Hit: 6 (1d8 + 2) piercing damage.
Monster Manual (2014), p. 309