Innate Spellcasting (Anathema ascendant Form Only). The anathema's innate spellcasting ability is Charisma (spell save DC 18). It can innately cast the following spells, requiring no material components:

At will: animal friendship (snakes only)

3/day each: darkness, entangle, fear, haste, suggestion, polymorph

1/day: Abi-Dalzim's horrid wilting, divine word, [Tooltip Not Found] (see Appendix C. New Spells)

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 its turn within 30 feet of the anathema and can see or hear it must succeed on a DC 18 Wisdom saving throw or become frightened of snakes and yuan-ti. A frightened target can repeat the saving throw at the end of each of its 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.

Regeneration. The anathema regains 10 hit points at the start of its turn if it has at least 1 hit point. If the anathema takes radiant damage, this trait doesn't function at the start of the anathema's next turn. The anathema is destroyed only if it starts its turn with 0 hit points and doesn't regenerate.

Shapechanger. The anathema can use its action to polymorph into a Huge anathema constrictor 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.

Six Heads. The anathema has advantage on Wisdom (Perception) checks and on saving throws against being blinded, charmed, deafened, frightened, stunned or knocked unconscious.

Multiattack (Anathema ascendant Form Only). The anathema makes two claw attacks, one constrict attack, and one Flurry of Bites attack.

Claw (Anathema ascendant Form Only). Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 14 (2d6 + 7) slashing damage.

Constrict. Melee Weapon Attack: +12 to hit, reach 15 ft., one Large or smaller creature. Hit: 17 (3d6 + 7) bludgeoning damage plus 7 (2d6) acid damage, and the target is grappled (escape DC 16). Until this grapple ends, the target is restrained and takes 17 (3d6 + 7) bludgeoning damage plus 7 (2d6) acid damage at the start of each of its turns, and the anathema can't constrict another target.

Flurry of Bites. Melee Weapon Attack: +12 to hit, reach 10 ft., one creature. Hit: 28 (6d6 + 7) piercing damage plus 14 (4d6) poison damage.

The anathema can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The anathema regains spent legendary actions at the start of its turn.

Move. The anathema moves up to half its speed.

Claw. The anathema makes a claw attack.

Constrict (Costs 2 Actions). The anathema makes a constrict attack.

Cast a Spell (Costs 3 Actions). The anathema casts a spell from its list of innate spells, using a spell slot as normal.

Command Yuan-ti (Costs 3 Actions). The anathema chooses up to three allied yuan-ti it can see within 60 feet of it. If the target can see and hear the anathema, the target can move up to half its speed and make one weapon attack as a reaction.