Yuan-Ti Anathema

Yuan-Ti Anathema CR: 12

Huge monstrosity (shapechanger, yuan-ti), neutral evil

Armor Class: 16 (natural armour)

Hit Points: 189 18d12+72

Speed: 40 ft , swim: 30 ft , climb: 30 ft

STR

23 +6

DEX

13 +1

CON

19 +4

INT

19 +4

WIS

17 +3

CHA

20 +5

Skills: Perception +7, Stealth +5

Damage Resistances: Acid, Fire, Lightning

Damage Immunities: Poison

Condition Immunities: Poison

Senses: Blindsight 30 ft, Darkvision 60 ft, passive Perception 17

Languages: Abyssal, Common, Draconic

Challenge Rating: 12

Innate Spellcasting (Anathema Form Only). The anathema's innate spellcasting ability is Charisma (spell save DC 17, it can innately cast the following spells, requiring no material components.

At will: Animal Friendship (snakes only).

1/day: Divine Word.

3/day: Darkness, Entangle, Fear, Haste, Suggestion, Polymorph.

Magic Resistance. The anathema has advantage on saving throws against spells and other magical effects.
Ophidiophobia Aura. Any creature of the anathema's choice, other than a snake or a yuan-ti, that starts it's turn within 30 ft of the anathema and can see or hear it must succeed on a DC 17 Wisdom saving throw, or become frightened of snakes and yuan-ti. A frightened frightened target can repeat the saving throw at the end of each of it's turns, ending the effect on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune to this aura for the next 24 hours.
Shapechanger. The anathema can use it's action to polymorph into a Huge giant constrictor snake, or back into it's true form. It's statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed.
Six Heads. The anathema has advantage on Wisdom (Perception) checks and on saving throws against being blinded, charmed, deafened, frightened, stunned, or knocked unconscious.

Actions

Multiattack (Anathema Form Only). The anathema makes two claw attacks, one constrict attack, and one Flurry of Bites attack.
Claw. Melee Weapon Attack +10 to hit, reach 10 ft, one target. Hit 13 2d6+6 slashing damage.
Constrict. Melee Weapon Attack +10 to hit, reach 15 ft, one target. Hit 16 3d6+6 bludgeoning damage plus 7 2d6 acid damage and the target is grappled (escape DC 16). Until the grapple ends, the target is restrained and takes 16 3d6+6 bludgeoning damage plus 7 2d6 acid damage at the start of each of it's turns, and the anathema can't constrict another target.
Flurry of Bites. Melee Weapon Attack +10 to hit, reach 10 ft, one creature. Hit 27 6d6+6 piercing damage 14 4d6 poison damage.

Anathema is the ultimate form of Yuan-Ti. An abomination that has sacrificed countless slaves, bathed in countless snakes, performed countless acts of cannibalism, all these are needed with the blackest of magic to transform it into an Anathema. Each is noticeable by being the largest of their species, with multiple snake heads, and a pair of arms ending in clawed hands. Scales cover every inch of it's body.

Suggested Environments

Tropical & Sub-tropical regions.