Shapechanger. The yuan-ti can use its action to polymorph into a Large 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.

Firearms Knowledge. The yuan-ti’s mastery of its weapons enables it to ignore the loading property of any firearm.

Innate Spellcasting (Abomination Form Only). The yuan-ti’s innate spellcasting ability is Charisma (spell save DC 15). The yuan-ti can innately cast the following spells, requiring no material components:

At will: animal friendship (snakes only)

3/day: suggestion

1/day: fear

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

Steady as She Goes. On the deck of a ship, the yuan-ti has advantage on ability checks and saving throws made against effects that would knock it prone or shove it overboard.

Multiattack (Abomination 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. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 7 (1d6 + 4) piercing damage plus 10 (3d6) poison damage.

Constrict. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 11 (2d6 + 4) 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 (Abomination Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage.

Laser Rifle (Abomination Form Only). Ranged Weapon Attack: +6 to hit, range 100/300 ft., one target. Hit: 12 (3d8 + 3) radiant damage.

Force Grenade (Abomination Form Only). The yuan-ti throws a grenade up to 60 feet, and the grenade explodes in a 20-foot-radius sphere. Each creature in that area must make a DC 15 Dexterity saving throw, taking 17 (5d6) force damage on a failed save, or half as much damage on a successful one. After the yuan-ti throws the grenade, roll a d6; on a roll of 4 or lower, the yuan-ti has no more grenades to throw.