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

While in bat form, Strahd can't speak, its walking speed is 5 feet, and it has a flying speed of 30 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 its true form if it dies.

While in mist form, Strahd 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 Strahd fails a saving throw, he can choose to succeed instead.

Misty Escape. When he drops to 0 hit points outside its resting place, Strahd 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 its 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.

Regeneration. Strahd regains 25 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 Strahd takes radiant damage or damage from holy water, this trait doesn't function at the start of Strahd's next turn.

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

Unholy Persistence. Strahd has advantages on saving throws against effects that turn undead.

Spellcasting. Strahd is an 18th-level spellcaster. His spellcasting ability is Intelligence (DC 19, +11 to hit with spell attacks). He has the following wizard spells prepared:

Cantrips (at will):fire bolt, toll the dead, chill touch, ray of frost, shocking grasp

1st level (4 slots): shield, witch bolt, cause fear, thunderwave

2nd level (3 slots): crown of madness, hold person, misty step

3rd level (3 slots): bestow curse, vampiric touch, lightning bolt

4th level (3 slots): greater invisibility, polymorph, evard's black tentacles

5th level (3 slots): cone of cold, dominate person

6th level (1 slot): chain lightning, create undead

7th level (1 slot): delayed blast fireball, reverse gravity

8th level (1 slot): dominate monster, feeblemind

9th level (1 slot): power word kill

Vampire Weaknesses. Strahd has the following flaws:

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

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

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

Sunlight Hypersensitivity. Strahd takes 20 radiant damage when it starts its turn in sunlight. While in sunlight, it has disadvantage on attack rolls and ability checks.