Shapechanger. If Vlad the Inhaler 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, Vlad the Inhaler 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, Vlad the Inhaler can't take any actions, speak, or manipulate objects.  The cloud does make A wheezing noise whule it moves. It is weightless, has a flying speed of 25 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.

Misty Escape. When it drops to 0 hit points outside its resting place, Vlad the Inhaler transforms into a cloud of mist (as in the Shapechanger trait) instead of falling unconscious, provided that it isn't in sunlight or running water. 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 resting place within 2 hours or be destroyed. Once in its resting place, it reverts to its vampire form. It is then paralyzed until it regains at least 1 hit point. After spending 1 hour in its resting place with 0 hit points, it regains 1 hit point.  Vlad the Inhaler's Asthma resets after regaining 1 hp.

Vlad's Legendary Resistance (3/Day). If Vlad the Inhaler fails a saving throw, it can choose to succeed instead.  Legendary Resistance iss useless against Asthma.

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

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

Asthma. Vlad the Inhaler suffers from debilitating Asthma and must use its inhaler to regain spent legendary action points, and stay alive.  If Vlad is exposed to Garlic, hay, or uses the dash action he will suffer level 3 exhaustion. If Vlad does not use his inhaler once every 12 hours, he will suffer level 4 exhaustion.  If he does not use his inhaler in a 24 hour period Vlad the Inhaler will fall to 0 hp, and revert to mist form. All exhaustion levels are removed when the inhaler is used. 

Vampire Weaknesses. Vlad the Inhaler has the following flaws:

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

Harmed by Running Water. Vlad the Inhaler 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 Vlad the Inhaler's heart while the vampire is incapacitated in its resting place, the vampire is paralyzed until the stake is removed.

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

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

Unarmed Strike (Vampire Form Only). Melee Weapon Attack: +10 to hit, reach 5 ft., one creature. Hit: 8 (1d8 + 5) bludgeoning damage. Instead of dealing damage, Vlad the Inhaler can grapple the target (escape DC 18).

Inhaler Strike (Vampire Form Only). Melee Weapon Attack: +10 to hit, reach 5 ft., one creature. Hit: 15 (4d4 + 5) bludgeoning damage. 

Bite. (Bat or Vampire Form Only). Melee Weapon Attack: +10 to hit, reach 5 ft., one willing creature, or a creature that is grappled by Vlad the Inhaler, 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 Vlad the Inhaler 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 Vlad the Inhaler's control.

Charm. Vlad the Inhaler targets one humanoid it can see within 30 feet of it. If the target can see Vlad the Inhaler, the target must succeed on a DC 16 Wisdom saving throw against this magic or be charmed by Vlad the Inhaler. The charmed target regards Vlad the Inhaler as a trusted friend to be heeded and protected. Although the target isn't under Vlad the Inhaler's control, it takes Vlad the Inhaler's requests or actions in the most favorable way it can, and it is a willing target for Vlad the Inhaler's bite attack.

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

Use Inhaler. Vlad the Inhaler pulls out a medicinal inhaler, places to his mouth and inhales.  Vlad the Inhaler regains all legendary action point, and regains 10hp, regardless if in sunlight. 

Spray in The Eyes.  (Vlad must have his inhaler on person)  If a creature attempts to grapple, disarm, or steal anything from Vlad the Inhaler and fail they must make a dc 13 constitution savingthrow.  On a fail he will spray his Inhaler into the creature's eyes blinding them for one turn.

Vlad the Inhaler can take 5 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. Vlad the Inhaler regains spent legendary actions after taking the use inhaler action.

Move. Vlad the Inhaler moves up to its speed without provoking opportunity attacks.

Unarmed Strike. Vlad the Inhaler makes one unarmed strike.

Bite.(Costs 2 Actions). Vlad the Inhaler makes one bite attack.