Carmilla

 Call to Lightning (Mythic Trait; recharges on a short or long rest). When the vampire is reduced to half of her hit points she enters a hastened state, her body arcing with electricity. While in this state she gains the following benefits:

• All movement speed increased by 30 feet and her movement doesn't provoke attacks of opportunity.
• She gains an additional attack on her turn.

This state lasts for 1 minute.

Legendary Resistance (3/Day). If the vampire fails a saving throw, she can choose to succeed instead.

Magic Weapon. The vampire's weapon attacks are magical.

Reactive. The vampire can take a reaction each turn in combat.

Regeneration. The vampire regains 20 hit points at the start of its turn if she 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. The vampire can walk difficult surfaces, including upside down on ceilings, without needing to make an ability check. She keeps her hands free for this, thus being able to wield weapons while climbing.

Vampire Weaknesses. The vampire has the following flaws:

Forbiddance. The vampire can’t enter a residence without an invitation from one of the occupants.

Harmed by Running Water. The vampire has disadvantage on all rolls while in running water.

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

Sunlight Hypersensitivity. The vampire takes 20 radiant damage when she starts her turn in sunlight. While in sunlight, she has disadvantage on attack rolls and ability checks.

Multiattack. The vampire makes seven attacks, only one of which can be a bite attack.

Blood Sword. Melee Weapon Attack: +13 to hit, reach 5 ft., one target. Hit: 11 (1d8 + 7) slashing damage. Rolling a 20 on the attack roll causes that target take an extra 14 slashing damage. Roll a second d20, if the roll on this is 20 as well, a limb is lopped off of the target. If the target has no limbs, a portion of its body is lopped off instead.

Unarmed Strike. Melee Weapon Attack: +11 to hit, reach 5 ft., one creature. Hit: 9 (1d8 + 5) bludgeoning damage. Instead of dealing damage, the vampire can grapple the target (escape DC 19).

Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one willing creature, or a creature that is grappled by the vampire, 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 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. A humanoid slain in this way and then buried in the ground rises the following night as a vampire spawn under the vampire’s control.

Charm. The vampire targets one humanoid she can see within 30 feet of her. If the target can see the vampire, the target must succeed on a DC 19 Wisdom saving throw against this magic or be charmed by the vampire. The charmed target regards the vampire 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 it is a willing target for the vampire’s bite attack.

Each time the vampire or the vampire’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 the vampire is destroyed, is on a different plane of existence than the target, or takes a bonus action to end the effect.

Parry. The vampire adds 6 to her AC against one weapon attack that would hit her. To do so, the vampire must see the attacker and be wielding a melee weapon.

Riposte. Carmilla makes a melee attack against a creature within 5 feet of her that misses her with a melee attack.

The vampire 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 vampire regains spent legendary actions at the start of her turn.

Move. The vampire moves up to her speed without provoking opportunity attacks.

Unarmed Strike. The vampire makes one unarmed strike.

Slash (Costs 2 Actions). The vampire makes one attack with her blood sword.

While in her mythic state, the vampire can use the following actions as though they were legendary actions.

Blood Ribbon (Costs 2 Actions). The vampire flashes out with her sword around her, lacerating anything nearby. Any creature within 10 feet of the vampire must make a DC 21 Dexterity saving throw or suffer 21 (6d6) slashing damage.

**** You (Costs 3 Actions). In a last ditch effort to deprive her foes of victory, the vampire plunges her blade into her heart, causing a catastrophic explosion. Each creature within 60 feet of the vampire must make a DC 17 Dexterity saving throw or suffer 36 (6d8) fire damage plus 36 (6d8) force damage plus 36 (6d8) thunder damage, or half as much on a save; constructs and structures take twice the damage from the thunder and force damage. Creatures within 10 feet of the vampire when she uses this ability have disadvantage on the saving throw. The vampire dies as part of this action, her body completely turned to ash.