Indomitable (2/Day). The yuan-ti rerolls a failed saving throw. It must use the new roll.

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.

Innate Spellcasting (Abomination Form Only). The yuan-ti’s innate spellcasting ability is Charisma (spell save DC 16). 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.

Spellcasting. The yuan-ti is a 17th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 16, +8 to hit with spell attacks). It has the following paladin spells prepared:

1st level (4 slots): command, compelled duel, thunderous smite

2nd level (3 slots): branding smite, hold person

3rd level (3 slots): dispel magic, haste

4th level (3 slots): banishment, staggering smite

5th level (1 slot): banishing smite, destructive wave

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: +9 to hit, reach 5 ft., one creature. Hit: 8 (1d6 + 5) piercing damage plus 10 (3d6) poison damage.

Constrict. Melee Weapon Attack: +9 to hit, reach 10 ft., one target Hit: 12 (2d6 + 5) bludgeoning damage, and the target is grappled (escape DC 16). Until this grapple ends, the target is restrained, and the yuan-ti can't constrict another target

Scimitar (Abomination Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) slashing damage.

Longbow (Abomination Form Only). Ranged Weapon Attack: +6 to hit, range 150/600 ft., one target. Hit: 11 (2d8 + 2) piercing damage plus 10 (3d6) poison damage.

Smite (1/Turn). As a bonus action, when the yuan-ti hits a creature with a weapon attack, it can expend a 1st level spell slot to deal 2d8 radiant or necrotic damage to the target. If the yuan-ti expends a spell slot of 2nd level or higher, the extra damage increases by 1d8 for each level above 1st (maximum 5d8).