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). Melee or Ranged Attack Roll: +5, reach 5 ft. or range 120 ft. Hit: 12 (2d8 + 3) Poison damage.
Constrict. Strength Saving Throw: DC 13, one Medium or smaller creature within 5 feet. Failure: 21 (4d8 + 3) Bludgeoning damage. The target has the Grappled condition (escape DC 13), and it has the Restrained condition until the grapple ends.
Spellcasting (Yuan-ti Form Only). The yuan-ti casts one of the following spells, requiring no Material components and using Wisdom as the spellcasting ability (spell save DC 13):
At will: Animal Friendship (snakes only)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.
