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

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

Vampire Weaknesses. Volenta has the following flaws:

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

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

Stake to the Heart. Volenta  is destroyed if a piercing weapon made of wood is driven into its heart while it is incapacitated in its resting place.

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

Reckless Attack  Volenta can throw aside all concern for defense to attack with fierce desperation. When the Volenta makes her first attack on her turn, she can decide to attack recklessly. Doing so gives her advantage on melee weapon attack rolls using Strength during this turn, but attack rolls against her have advantage until her next turn.

Danger Sense Volenta has advantage on Dexterity saving throws against effects that she can see, such as traps and spells. To gain this benefit, she can’t be blinded, deafened, or incapacitated.

Frenzy  Volenta can go into a frenzy when she rages. If she does so, for the duration of the rage she can make a single melee weapon attack as a bonus action on each of its turns after this one. When her rage ends, Volenta suffers one level of exhaustion.

Mindless Rage Volenta can’t be charmed or frightened while raging. If she is charmed or frightened when she enters her rage, the effect is suspended for the duration of the rage.

Feral Instincts Volenta's instincts are so honed that she has advantage on initiative rolls.

Additionally, if she is surprised at the beginning of combat and isn't incapacitated, she can act normally on her first turn, but only if she enters her rage before doing anything else on that turn.

A Husband's Gift Her wedding gift from Strahd is a small amulet around her neck that is the same magic he composed his crystal heart from (it is the prototype he developed though she believes it to be an item of deep value to him). It can absorb 20 damage dealt to her before shattering. If it shatters she goes into a frenzy rage immediately. 

Multiattack. Volenta makes three attacks, four when frenzied,  only one of which can be a bite attack. 

Claws. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 9 (2d4 + 4), +2 when raging, slashing damage. Instead of dealing damage, the Volenta can grapple the target (escape DC 15).

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one willing creature, or a creature that is grappled by the vampire, incapacitated, or restrained. Hit: 7 (1d6 + 4) piercing damage, +2 when raging, plus 7 (2d6) 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. 

Great Sword. Melee Weapon Attack: +7, reach 5 ft., one creature. Hit: 13(2d6 + 4), +2 when raging.

Rage  (4 uses per long rest)  In battle, Volenta fights with primal ferocity. On its turn, it  can enter a rage as a bonus action.

While raging, she gains the following benefits if she isn't wearing heavy armor:

• She has advantage on Strength checks and Strength saving throws.
• When she makes a melee weapon attack using Strength, she gains +2 to the damage 
• She has resistance to bludgeoning, piercing, and slashing damage, even from magical attacks.

Volenta's rage lasts for 1 minute. It ends early if the Volenta is knocked unconscious or if her turn ends and she hasn't attacked a hostile creature since her last turn or taken damage since then. She can also end her rage on her turn as a bonus action.