Asoroth

Primordial Shape.  Asoroth is in most primordial form. He gains a flying speed of 60 feet and a walking speed of 50 feet. He is stronger in this form but his spell casting is hindered.

Magic Weapons. Asoroth's attacks are considered magical.

Regeneration. Asoroth regains 30 hit points at the start of his turn if he has at least 0 hit points.

Kin Killer. Asoroth can only be killed by other Higher Vampires. If he is dropped to 0 hit points from other means he will regenerate and re-establish his body even if a single amount of his body remains.

Spellcasting. Asoroth is 17th-level spellcaster. His spellcasting ability is Intelligence (spell save DC 18, +10 to hit with spell attacks). Asoroth has the following wizard spells prepared: 
Cantrips (at will): Mage Hand, Chill Touch, Ray of Frost
1st level (at will): False Life, Detect Magic, Shield
2nd level (at will): Darkness, Detect Thoughts, Mirror Image
3rd level (at will): Counterspell, Dispel Magic, Animate Dead
4th level (3 slots): Blight, Greater Invisibility, Black Tentacles
5th level (3 slots): Dominate Person, Animate Objects
6th level (3 slots): Circle of Death, Create Undead
7th level (2 slots): Finger of Death, Teleport
8th level (2 slots): Power Word Stun, Dominate Monster
9th level (2 slots): Gate, Time Stop

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

Special Weakness. Asoroth is weakened if he ingests undead blood. If ingested he is no longer resistant to non-magical attacks. 

Multiattack. Asoroth makes three melee attacks.

Unarmed Strike. Melee weapon attack: +16 to hit, reach 5 feet, one target. Hit 24 (5d8 +9) bludgeoning damage plus 9(3d6) necrotic damage. 

Bite. Melee weapon attack: +16 to hit, reach 5 feet, one willing creature or a creature grappled by Asoroth, incapacitated or restrained. Hit: 19(3d10 +9) piercing damage plus 20(5d8) necrotic damage. When Asoroth bites a creature, he steals 20 hit points and reduces the creature's total hit points by 20.

Claw. Melee weapon attack: +16 to hit 10 feet, one target. Hit: 28(4d12 +9) slashing damage plus 9(3d6) necrotic damage. If Asoroth grappled a creature he can attempt to rip the heart of the creature out. Roll to contest strength, if Asoroth wins, he rips the heart of the creature out and instantly kills them, regardless of hit points.

Charm. Asoroth targets one humanoid it can see within 60 feet of it. If the target can see Asoroth, the target must succeed on a DC 22 Wisdom saving throw against this magic or be charmed by Asoroth. The charmed target regards Asoroth as a trusted friend to be heeded and protected. Although the target isn't under Asoroth's control, it takes Asoroth's requests or actions in the most favorable way it can, and it is a willing target for Asoroth's bite attack. Each time Asoroth or its 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 Asoroth is destroyed, is on a different plane of existence than the target, or takes a bonus action to end the effect.

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Legendary Resistance (3/Day). If Asoroth fails, a saving throw, he can choose to succeed instead.

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