Vampiric Lord

Shapechanger. If the archvampire isn't in sunlight or running water, it can use its action to polymorph into a Tiny bat, a Medium wolf, or a Medium cloud of mist, or back into its true form.

While in bat or wolf form, the archvampire can't speak. In bat form, its walking speed is 5 feet, and it has a flying speed of 30 feet. In wolf form, its walking speed is 40 feet. Its statistics, other than its size and speed, are unchanged. Anything it is wearing transforms with it, but nothing it is carrying does. It reverts to his true form if he dies.

While in mist form, the archvampire can't take any actions, speak, or manipulate objects. It 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 the archvampire fails a saving throw, it can choose to succeed instead.

Magic Weapons. The archvampire's weapon attacks are considered magical for overcoming resistances.

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

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

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

Spellcasting. The archvampire is a 10th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 20, +12 to hit with spell attacks). The archvampire has the following wizard spells prepared:

Cantrips (at will): chill touch, mage hand, message prestidigitation, ray of frost

1st level (4 slots): comprehend languages, fog cloud, sleep

2nd level (3 slots): detect thoughts, gust of wind, mirror image

3rd level (3 slots): animate dead, bestow curse, nondetection, vampiric touch

4th level (3 slots): blight, greater invisibility, polymorph

5th level (2 slots): animate objects, cloudkill, dominate person

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

Turn Resistance. The archvampire has advantage on saving throws against any effect that turns undead.

Vampire Weaknesses. The archvampire has the following flaws:

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

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

Stake to the Heart. If a piercing weapon made of wood is driven into the its heart while it is incapacitated in its place of rest, it is paralyzed until the stake is removed.

Sunlight Hypersensitivity. While in sunlight, the archvampire takes 20 radiant damage at the start of its turn, and it has disadvantage on attack rolls and ability checks.

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

Greatsword. (Vampire Form Only). Melee Weapon Attack. +14 to hit, reach 5 ft., one creature. Hit: 15 (2d6 + 8) slashing damage.

Unarmed Strike. (Vampire Form Only). Melee Weapon Attack: +11 to hit, reach 5 ft., one creature. Hit: 9 (1d8 + 5) bludgeoning damage plus 14 (4d6) necrotic damage. If the target is a creature, the archvampire can grapple it (escape DC 20) instead of dealing the bludgeoning damage.

Bite (Bat or Vampire Form Only). Melee Weapon Attack: +11 to hit, reach 5 ft., one willing creature, or a creature that is grappled by the archvampire, incapacitated, or restrained. Hit: 8 (1d6 + 5) piercing 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 archvampire 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. A humanoid slain in this way and then buried in the ground rises the following night as a vampire spawn under the archvampire's control.

Wolf Bite (Wolf Form Only). Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 10 (2d4 + 5) piercing damage. If the target is a creature, it must succeed on a DC 19 Strength saving throw or be knocked prone.

Charm. The archvampire targets one humanoid it can see within 30 feet of it. If the target can see the archvampire, the target must succeed on a DC 19 Wisdom saving throw against this magic or be charmed. The charmed target regards the archvampire as a trusted friend to be heeded and protected. Although the target isn't under the vampire's control, it takes the vampire's requests or actions in the most favorable way it can, and lets the archvampire bite it.

Each time the archvampire or its 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 archvampire 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). The archvampire magically calls 2d4 swarms of bats or rats (swarm of bats, swarm of rats), provided that the sun isn't up. While outdoors, the archvampire can call 3d6 wolves (wolf) instead. The called creatures arrive in 1d4 rounds, acting as allies of the archvampire and obeying its spoken commands. The beasts remain for 1 hour, until the archvampire dies, or until it dismisses them as a bonus action.

The archvampire 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. The archvampire regains spent legendary actions at the start of its turn.

Cantrip. The archvampire casts a cantrip.

Move. The archvampire moves up to its speed without provoking opportunity attacks.

Unarmed Strike. The archvampire makes one unarmed strike.

Bite. (Costs 2 Actions). The archvampire makes one bite attack.