Ailana, The Queen of Witches

 Shapechanger. If Ailana isn't in sunlight or running water, she can use her action to polymorph into a Tiny bat or a Medium cloud of mist, or back into her true form.
While in bat form, Ailana can't speak, its walking speed is 5 feet, and she has a flying speed of 30 feet. Her statistics, other than its size and speed, are unchanged. Anything she is wearing transforms with her, but nothing she is carrying does. She reverts to her true form if she dies.
While in mist form, Ailana can't take any actions, speak, or manipulate objects. She is weightless, has a flying speed of 20 feet, can hover, and can enter a hostile creature's space and stop there. In addition, if air can pass through a space, the mist can do so without squeezing, and it can't pass through water. It has advantage on Strength, Dexterity, and Constitution saving throws, and it is immune to all nonmagical damage, except the damage it takes from sunlight.

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

 Regeneration. Ailana regains 25 hit points at the start of her turn if she has at least 1 hit point and she isn't in sunlight or running water. If Ailana takes radiant damage or damage from holy water, she regains 10 hit points at the start of her turn instead.

Spider Climb. Ailana can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

 Sorcery Points. Ailana has 20 sorcery points she can spend to use her metamagic options.

Metamagic. Ailana can use the following metamagic spending the corresponding sorcery points : 

Heightenned Spell: When Ailana casts a spell that forces a creature to make a saving throw to resist its effects, she can spend 3 sorcery points to give one target of the spell disadvantage on its first saving throw made against the spell.

Quickened Spell:  When Ailana casts a spell that has a casting time of 1 action, she can spend 2 sorcery points to change the casting time to 1 bonus action for this casting.

Subtle Spell: When Ailana casts a spell, she can spend 1 sorcery point to cast it without any somatic or verbal components.

Twinned Spell:  When Ailana casts a spell that targets only one creature and doesn't have a range of self, she can spend a number of sorcery points equal to the spell's level to target a second creature in range with the same spell (1 sorcery point if the spell is a cantrip). To be eligible for Twinned Spell, a spell must be incapable of targeting more than one creature at the spell's current level.

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

Otherworldy Wings. Using a bonus action, Ailana can manifest a pair of bat wings from her back. While the wings are present, she has a flying speed of 30 feet. The wings last until she's incapacitated, she dies, or dismisses them as a bonus action.

Unearthly Recovery. As a bonus action when Ailana has less than half of her hit points remaining, she can regain a number of hit points equal to half her hit point maximum.

Spellcasting. Ailana is an 20th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 19, +11 to hit with spell attacks). 

Cantrips (at will): fire bolt, toll the dead, mage hand, prestidigitation, shocking grasp

1st level (4 slots): detect magic, identify, mage armor, shield

2nd level (3 slots): spiritual weapon, mirror image, misty step

3rd level (3 slots): counterspell, fly, lightning bolt

4th level (3 slots): banishment, fire shield, freedom of movement

5th level (3 slots): cone of cold, scrying, wall of force

6th level (1 slot): globe of invulnerability, harm

7th level (1 slot): power word pain, divine word 

8th level (1 slot): power word stun

9th level (1 slot): imprisonment

 Multiattack (Vampire Form Only). Ailana makes two attacks, only one of which can be a bite attack.

Unarmed Strike (Vampire Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one creature. Hit: (1d8 + 4) bludgeoning damage. Instead of dealing damage, Ailana can grapple the target (escape DC 18)

Bite (Bat or Vampire Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one willing creature, or a creature that is grappled by the Ailana, incapacitated, or restrained. Hit: (1d6 + 4) piercing damage plus (3d6)necrotic damage. The target's hit point maximum is reduced by an amount equal to the necrotic damage taken, and the vampire regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0. A humanoid slain in this way and then buried in the ground rises the following night as a vampire spawn under the vampire's control.

Charm. Ailana targets one humanoid it can see within 30 ft. of it. If the target can see Ailana, the target must succeed on a DC 19 Wisdom saving throw against this magic or be charmed by Ailana. The charmed target regards Ailana as a trusted friend to be heeded and protected. Although the target isn't under the Ailana's control, it takes Ailana's requests or actions in the most favorable way it can, and it is a willing target for the Ailana's bit attack.
Each time Ailana or the Ailana's companions do anything harmful to the target, it can repeat the saving throw, ending the effect on itself on a success. Otherwise, the effect lasts 24 hours or until the Ailana is destroyed, is on a different plane of existence than the target, or takes a bonus action to end the effect.

Children of the Night (1/Day). Ailana magically calls 3d4 swarms of bats or rats, provided that the sun isn't up. While outdoors, the vampire can call 4d6 wolves instead. The called creatures arrive in 1d4 rounds, acting as allies of Ailana and obeying her spoken commands. The beasts remain for 1 hour,  until Ailana dies, or until Ailana dismisses them as a bonus action.

• Move. Ailana moves up to her speed without provoking opportunity attacks.
• Unarmed Strike. Ailana makes one unarmed strike.
• Bite (Costs 2 Actions).Ailana makes one bite attack.
• Cast Cantrip. Ailana casts a cantrip from the list of her prepared spells.