Buhguul

Demonic Weapons. Buhguul weapon attacks are magical. When Buhguul hits with any weapon, the weapon deals an extra 8d8 necrotic damage (included in the attack).

Fear Aura.Any creature hostile to the Buhguul that starts its turn within 20 feet of the Buhguul must make a DC 18 Wisdom saving throw, unless the Buhguul is incapacitated On a failed save, the creature is frightened until the start of its next turn. If a creature's saving throw is successful, the creature is immune to the Buhguul Fear Aura for the next 24 hours

Limited Magic Immunity. Buhguul can’t be affected or detected by spells of 6th level or lower unless he wishes to be. He has advantage on saving throws against all other spells and magical effects.

Regeneration.Buhguul  regains 20 hit points at the start of its turn. If it takes Cold or radiant damage, this trait doesn’t function at the start of its next turn. Buhguul dies only if it starts its turn with 0 hit points and doesn’t regenerate.

Rejuvenation. Buhguul body turns to dust when he drops to 0 hit points, and his equipment is left behind. Buhguul gains a new body after 1d10 days, regaining all his hit points and becoming active again. The new body appears within 5 feet of Buhguul phylactery, the location of which is hidden.

Master of Undeath.When Buhguul casts animate dead or create undead, he chooses the level at which the spell is cast, and the creatures created by the spells remain under his control indefinitely. Additionally, he can cast create undead even when it isn’t night.

 At will: animate dead,create undead 

Multiattack. Buhguul makes three greatsword attacks.

Greatsword.Melee Weapon Attack: +15 to hit, reach 15 ft., one target. Hit: 22 (6d6 + 8) slashing damage plus 27 (8d8) Necrotic damage.

Hellfire Orb (1/Day). Buhguul hurls a magical ball of fire that explodes at a point it can see within 120 feet of it. Each creature in a 20-foot-radius sphere centered on that point must make a DC 18 Dexterity saving throw. The sphere spreads around corners. A creature takes 35 (10d6) fire damage and 35 (10d6) necrotic damage on a failed save, or half as much damage on a successful one.

Teleport. Buhguul magically teleports, along with any equipment he is wearing or carrying, up to 120 feet to an unoccupied space he can see.

Savage (Costs 2 Actions). Buhguul makes a greatsword attack against each creature within 10 feet of him.

Creeping Death (Costs 2 Actions). Buhguul chooses a point on the ground that he can see within 100 feet of him. A cylinder of swirling necrotic energy 60 feet tall and with a 10-foot radius rises from that point and lasts until the end of Buhguul next turn. Creatures in that area are vulnerable to necrotic damage.

Provoke Rage (Costs 3 Actions). Each creature within 60 feet of Buhguul must succeed on a DC 18 Wisdom saving throw or use its reaction to make a melee weapon attack against a random creature within reach. If no creatures are within reach, it makes a ranged weapon attack against a random creature within range, throwing its weapon if necessary. This attack is made with advantage and gains a +4 bonus to the damage roll.