Innate Spellcasting (Anathema Form Only). Wąż’s innate spellcasting ability is Charisma (spell save DC 18). He can innately cast the following spells, requiring no material components:
At will: animal friendship (snakes only), poison spray
3/day each: darkness, entangle, fear, haste, suggestion, polymorph
1/day: divine word
Magic Resistance. Wąż has advantage on saving throws against spells and other magical effects.
Ophidiophobia Aura. Any creature of Wąż’s choice, other than a snake or a yuan-ti, that starts its turn within 30 feet of him and can see or hear him 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.
Shapechanger. Wąż can use his action to polymorph into a Huge giant 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.
Shadow Sorcerer. Wąż is an 11th level Shadow Sorcerer, with 11 Sorcery Points, the Empowered, Quickened, and Twinned metamagics, a Spell Save DC of 18, and the following spells.
Cantrips(6): acid splash, chill touch, fire bolt, infestation, lightning lure, ray of frost
1st Level(4 slots): chaos bolt, detect magic, ice knife, shield
2nd Level(3 slots): hold person
3rd Level(3 slots): counterspell, fireball, slow
4th Level(3 slots): sickening radiance
5th Level(2 slots): cloudkill, contagion
6th Level(1 slot): disintegrate
Serpent of Ill Omen. As a bonus action, you can spend 3 sorcery points to summon a giant constrictor snake. The snake can move through objects and creatures as if it were difficult terrain. The snake takes 5 force damage if it ends its turn in another creature or object's space. The snake spawns with temporary hit points equal to half of Wąż's Sorcerer Level(5).
Multiattack (Anathema Form Only). The anathema makes two claw attacks, one constrict attack, and one Flurry of Bites attack.
Claw (Anathema Form Only). Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 13 (2d6 + 6) slashing damage plus 3 (1d6) acid damage.
Constrict. Melee Weapon Attack: +10 to hit, reach 15 ft., one Large or smaller creature. Hit: 16 (3d6 + 6) 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 16 (3d6 + 6) 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: +10 to hit, reach 10 ft., one creature. Hit: 27 (6d6 + 6) piercing damage plus 14 (4d6) poison damage.
Counterspell
Attack of Opportunity(Sentinel)
Sentinel Attack
3 legendary actions.
Claw attack(1 action)
Cantrip(1 action)
Spell(2 actions)