Armor Class 12
Hit Points 66 (12d8 + 12)
Speed 30 ft., climb 30 ft.
Skills Stealth +4 (+6 while in snake form)
Damage Immunities poison
Condition Immunities poisoned
Senses Darkvision 60 ft., passive Perception 13
Languages Abyssal, Common, Draconic
Challenge 3
Magic Resistance. The yuan-ti has Advantage on saving throws against spells and other magical effects.
Multiattack. The yuan-ti makes two Poison Burst attacks, and it can use Spellcasting to cast Suggestion if available.
Poison Burst (Yuan-ti Form Only). m,r +5, reach 5 ft. or range 120 ft. Hit: 12 (2d8 + 3) Poison damage.
Constrict. str DC 13, one Medium or smaller creature within 5 feet. 21 (4d8 + 3) Bludgeoning damage. The target has the Grappled condition (escape DC 13), and it has the Restrained condition until the grapple ends.
Shape-Shift. The yuan-ti shape-shifts into a Medium snake or returns to its true form. If it dies, it stays in its current form. The yuan-ti's game statistics are the same in each form, except where noted. Any equipment it is wearing or carrying isn't transformed.
Monster Manual (2024), p. 344