Crystal Yuan-ti Anathema

Innate Spellcasting (True 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: stone shape, scrying, maximilian’s earthen grasp

3/day each: flesh to stone, bestow curse, mirror image, suggestion, telekinesis

1/day: imprisonment (Minimus Containment inside a gemstone only, and there can be only one captive at a time).

Magic Resistance. The anathema has advantage on saving throws against spells and other magical effects.

Magic Weapons. The anathema's weapon attacks are considered magical.

Refraction. Any time the anathema is targeted by a magic missile spell, a line spell, or a spell that requires a ranged attack roll, roll a d6. On a 1 to 3, the anathema is unaffected. On a 4 to 5, the anathema is unaffected, and the effect is reflected onto a random creature within that spell's range as if it originated from the anathema. On a 6, the anathema is unaffected, and the effect is reflected back at the caster as though it originated from the anathema, turning the caster into the target.

Earth Glide. The anathema can burrow through crystal, as well as nonmagical earth and stone. While doing so, the anathema doesn't disturb the material it moves through.

Shapechanger. The anathema can use its action to polymorph into a Huge giant constrictor snake made of crystal with an AC of 18, 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 Form Only). The anathema makes four claw attacks and one constrict attack.

Claw (Anathema Form Only). 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 Large or smaller creature. Hit: 23 (5d6 + 6) bludgeoning damage, and the target is grappled (escape DC 16). Until this grapple ends, the target is restrained and takes 23 (5d6 + 6) bludgeoning damage at the start of each of its turns, and the anathema can’t constrict another target.

Prism Beam (Recharge 5/6). The anathema's dense core ignites with technicolor light, which warbles and brightens before unleashing a ray of deadly incandescence. The anathema casts Prismatic Spray.