Your Strength and Charisma increases by 2. Your Dexterity decreases by 2.

Anathema don't age, allowing them to pursue their goals until the end of days. Truly powerful Anathema can rule multiple cities and bring entire regions under their control.

Anathema usually view themselves as demigods, they use others for their own ends and are as such usually lean neutral evil.

This typically only applies to Anathema who willingly transformed, it is possible to be not be willingly transformed and as such, an Anathema can vary in alignment depending on their past.

Anathema range from either 8-16 ft or 16-32 ft. Depending on which you choose, you are either Large or Huge.

The ascension to divinity has made your eyes far greater than normal. You have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

Any creature of the Anathema's choice, other than a snake or a Yuan-ti, that starts its turn within 30 ft of the Anathema and can see or hear it must succeed on a DC 17 Wisdom save 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 a success. On success, the target is immune to this for 24 hours. The Anathema can only use this trait once per day.

At 3rd level, the Anathema can use this trait once per day plus halve of the Anathema's Charisma Modifier

At 6th level, the Anathema can use this trait once per day plus the Anathema's Charisma Modifier

As an action, the Anathema can use its action to poly-morph into a huge constrictor snake or back into its true form. Any equipment it is wearing or carrying isn't transformed.

At 1st level, the Yuan-ti Anathema can only transform between it's Pureblood disguise or it's true form. As a Pureblood, the Anathema's Ophidiophobia Aura and Six Heads aren't active.

At 6th level, the Yuan-ti Anathema gains the ability to transform into a huge constrictor snake. This form cannot use spells, features etc that involves arms. The Anathema's Flurry of Bites deals +12 piercing damage instead of +6.

You have advantage on Perception checks and on saving throws against being blinded, charmed, deafened, frightened, stunned, or knocked unconscious.

The Anathema slashes at a foe with it's claws.

Melee Weapon Attack, reach 10 ft, one target. On Hit: 1d6 +6 slashing damage.

If The Anathema is in it's Pureblood form, the Anathema's hands transform into claws.

At 3rd level, Claws deals an extra 1d6 slashing damage.

The Anathema's tail coils around a target and constricts someone. Melee Weapon Attack, reach 15 ft, one creature that is one size category below the Yuan-ti Anathema or smaller. On Hit: 1d6 +6 bludgeoning damage plus 1d6 acid damage. The creature is grappled (escape DC 16), and until this grapple ends, the target takes 1d6 +6 bludgeoning damage plus 1d6 acid damage at the start of each of it's turns and the Yuan-ti Anathema cannot attack another creature with Constrict. Constrict can only be used once per 2 rounds.

At 3rd level, Constrict deals an extra 1d6 bludgeoning and acid damage.

At 6th level, Constrict deals an extra 1d6 bludgeoning and acid damage.

The Anathema's six heads attack a foe all at once. Melee Weapon Attack, reach 10 ft, one creature. On Hit: 3d4 +3 piercing damage plus 3d4 +3 poison damage. The Yuan-ti Anathema can only use Flurry of Bites once per 2 rounds.

At 3rd level, Flurry of Bites deals 6d4 +6 piercing damage plus 6d4 +6 poison damage instead.

At 6th level, Flurry of Bites deals 6d6 +6 poison damage instead of 6d4 +6.

At 9th level, Flurry of Bites deals 6d6 +6 piercing damage instead of 6d4 +6.