Axihuatl, the Proselyte of the Court

Special Equipment. Axihuatl wears a ring of protection (accounted for in her statistics).

Shapechanger. Axihuatl can use her action to polymorph into a form that resembles a Medium humanoid, or back into her true form. Aside from her size and the walking speed of her new form, her statistics are the same in each form. Any equipment she is wearing or carrying isn't transformed.

Legendary Resistance (3/Day). If Axithuatl fails a saving throw, she can choose to succeed instead.

Spellcasting. Axihuatl is an 8th-level spellcaster. Her spellcasting ability is Wisdom (spell save DC 17, +9 to hit with spell attacks). Axihuatl has the following cleric spells prepared:

Cantrips (at will): guidance*, spare the dying*, thaumaturgy, toll the dead*
1st level (4 slots): bane*, charm person*, command, inflict wounds*
2nd level (3 slots): blindness/deafness, hold person*, silence*
3rd level (3 slots): counterspell*, vampiric touch*, lightning bolt*
4th level (2 slots): blight*, control water*

(* These spells require somatic components and cannot be cast while Axihuatl is in her natural form.)

Two Minds of Madness. Axihuatl has advantage on all Intelligence, Wisdom, and Charisma saving throws.

Regeneration. Axihuatl regains 10 hit points at the start of her turn. If Axihuatl takes acid or fire damage, this trait doesn't function at the start of Axihuatl's next turn. Axihuatl dies only if she starts her turn with 0 hit points and doesn't regenerate.

Multiattack. While in her natural form, Axihuatl can make two attacks with her Vampiric Bite.

Vampiric Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 7 (2d6 + 1) piercing damage. The target must succeed on a DC 17 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken, and Axihuatl regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if its hit point maximum is reduced to 0.

Barbed Tail. When a creature provokes an opportunity attack from Axihuatl, she can make the following attack instead of using her bite.

Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 9 (1d10 + 4) piercing damage.

Axihuatl 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. Axihuatl regains spent legendary actions at the start of her turn.

Detect. Axihuatl makes a Wisdom (Perception) check.

Teleport (Costs 2 Actions). Axihuatl magically teleports, along with any equipment she is wearing or carrying, up to 120 feet to an unoccupied space she can see.

Barbed Tail (Costs 2 Actions). Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 9 (1d10 + 4) piercing damage.