Anton Delascoshen

Shapechanger. If Anton isn't in sunlight or running water, he can use his action to polymorph into a tiny bat or a medium cloud of mist, or back into his true form.

While in bat form, Anton can't speak, his walking speed is 5 feet, and he has a flying speed of 30 feet. His statistics, other than his size and speed, are unchanged. Anything he is wearing transforms with him, but nothing he is carrying does. Anton reverts to his true form if he dies.

While in mist form, the Anton can't take any actions, speak, or manipulate objects. He 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, Anton can do so without squeezing, and he can’t pass through water. Anton has advantage on Strength, Dexterity, and Constitution saving throws, and he is immune to all nonmagical damage, except the damage he takes from sunlight.

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

Misty Escape. When he drops to 0 hit points outside his resting place, Anton transforms into a cloud of mist (as in the Shapechanger trait) instead of falling unconscious, provided that he isn't in sunlight or running water. If he can't transform, he is destroyed.

While he has 0 hit points in mist form, he can't revert to his vampire form, and he must reach his resting place within 2 hours or be destroyed. Once in his resting place, he reverts to his vampire form. He is then paralyzed until he regains at least 1 hit point. After spending 1 hour in his resting place with 0 hit points, he regains 1 hit point.

Psychic Weapons. Anton's weapon attacks are magical, and deal an additional 7 (2d6) psychic damage on a hit (included in the attack). 

Regeneration. Anton regains 20 hit points at the start of his turn if he has at least 1 hit point and isn't in sunlight or running water. If Anton takes radiant damage or damage from holy water, this trait doesn't function at the start of his next turn.

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

Vampire Weaknesses. Anton has the following flaws:

Forbiddance. Anton can't enter a residence without an invitation from one of the occupants.

Harmed by Running Water. Anton takes 20 acid damage if he ends its turn in running water.

Stake to the Heart. If a piercing weapon made of wood is driven into Anton's heart while he is incapacitated in his resting place, he is paralyzed until the stake is removed.

Sunlight Hypersensitivity. Anton takes 20 radiant damage when he starts his turn in sunlight. While in sunlight, he has disadvantage on attack rolls and ability checks.

Spellcasting. Anton is a 13th-level spellcaster. His spellcasting ability is Charisma (spell save DC 17, +9 to hit with spell attacks). Anton has the following spells prepared:

Cantrips (at will): friends, mage hand, minor illusion, vicious mockery
1st level (4 slots): charm person, disguise self, dissonant whispers, sleep
2nd level (3 slots): detect thoughts, invisibility, phantasmal force, suggestion
3rd level (3 slots): bestow curse, dispel magic, hypnotic pattern, nondetection
4th level (3 slots): charm monster, dimension door
5th level (3 slots): dream, modify memory
6th level (1 slot): eyebite, mass suggestion
7th level (1 slot): mordenkainen's magnificent mansion, project image

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

Claw (Vampire Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one creature. Hit: 8 (1d8 + 4) slashing damage and 7 (2d6) psychic damage. Instead of dealing damage, Anton 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 Anton, incapacitated, or restrained. Hit: 7 (1d6 + 4) piercing damage and 7 (2d6) psychic damage plus 10 (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. Anton targets one humanoid he can see within 30 feet of him. If the target can see the vampire, the target must succeed on a DC 17 Wisdom saving throw against this magic or be charmed by Anton. The charmed target regards Anton as a trusted friend to be heeded and protected. Although the target isn't under Anton's control, it takes Anton's requests or actions in the most favorable way it can, and it is a willing target for Anton's bite attack. 

Each time Anton or the Anton'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 Anton is destroyed, is on a different plane of existence than the target, or takes a bonus action to end the effect. 

Anton 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. Anton regains spent legendary actions at the start of his turn.

Skulk. Anton moves up to its speed without provoking opportunity attacks. If Anton ends this movement in an area of dim light or darkness, he becomes invisible until he moves, attacks or casts a spell. 

Bite (Costs 2 Actions). Anton makes one bite attack.

Spellcasting (Costs 3 Actions). Anton casts a spell that has a casting time of one action.