Vampire

If the monster fails a saving throw, it can choose to succeed instead.

If the monster drops to 0 Hit Points outside its resting place, the monster uses Shape-Shift to become mist (no action required). If it can't use Shape-Shift, it is destroyed.
While it has 0 Hit Points in mist form, it can't return to its vampire form, and it must reach its resting place within 2 hours or be destroyed. Once in its resting place, it returns to its vampire form and has the Paralyzed condition until it regains any Hit Points, and it regains 1 Hit Point after spending 1 hour there.

The monster can climb difficult surfaces, including along ceilings, without needing to make an ability check.

The monster has these weaknesses:
Forbiddance. The monster can't enter a residence without an invitation from an occupant.
Running Water. The monster takes 20 Acid damage if it ends its turn in running water.
Stake to the Heart. The monster is destroyed if a weapon that deals Piercing damage is driven into the monster's heart while the monster has the Incapacitated condition.
Sunlight. The monster takes 20 Radiant damage if it starts its turn in sunlight. While in sunlight, it has Disadvantage on attack rolls and ability checks.

The monster makes two Grave Strike attacks and uses Bite.

. . If the target is a Large or smaller creature, it has the Grappled condition (escape DC ) from one of two hands.

Constitution Saving Throw: DC , one within feet .
Failure: damage. The target's Hit Point maximum decreases by an amount equal to the Necrotic damage taken, and the monster regains Hit Points equal to that amount. A Humanoid reduced to 0 Hit Points by this damage and then buried rises the following sunset as a Vampire Spawn under the monster's control.

The monster casts @UUID[Compendium.dnd5e.spells24.Item.phbsplCharmPerso], requiring no spell components and using Charisma as the spellcasting ability (spell save DC ), and the duration is hours. The Charmed target is a willing recipient of the monster's Bite, the damage of which doesn't end the spell. When the spell ends, the target is unaware it was Charmed by the monster.

If the monster isn't in sunlight or running water, it shape-shifts into a Tiny bat (Speed 5 ft., Fly Speed 30 ft.) or a Medium cloud of mist (Speed 5 ft., Fly Speed 20 ft. [hover]), or it returns to its vampire form. Anything it is wearing transforms with it.
While in bat form, the monster can't speak. Its game statistics, other than its size and Speed, are unchanged.
While in mist form, the monster can't take any actions, speak, or manipulate objects. It is weightless and can enter an enemy's space and stop there. If air can pass through a space, the mist can do so, but it can't pass through liquid. It has Resistance to all damage, except the damage it takes from sunlight.