Lord of Evil. Zargothrax can gain control over any creature that has the Evil Alignment.

Spellcasting. Zargothrax is a 8-level spellcaster. Its spellcasting ability is Charisma (spell save DC 19, +11 to hit with spell attacks). Zargothrax has following Sorcerer spells prepared:
Cantrips (at will): Chill Touch, Fire Bolt, Light, Mage Hand, Ray of Frost, Shocking Grasp, True Strike
1st level (10 slots): Disguise Self, Magic Missile, Protection from Good and Evil, Sanctuary, Shield.

2nd level (8 slots): Lesser Restoration, Magic Missile, Pyrotechnics, Scorching Ray, Zone of Truth

3rd level (8 slots): Counterspell, Daylight, Fireball, Haste, Magic Missile, Scorching Ray

4th level (6 slots): Banishment, Counterspell, Fireball, Magic Missile, Scorching Ray

5th level (6 slots): Banishment, Counterspell, Fireball, Hold Monster, Insect Plague, Magic Missile, Scorching Ray

6th level (4 slots): Banishment, Circle of Death, Counterspell, Fireball, Hold Monster, Insect Plague, Magic Missile, Scorching Ray

7th level (4 slots): Banishment, Circle of Death, Counterspell, Fireball, Hold Monster, Insect Plague, Magic Missile, Scorching Ray

8th level (4 slots): Banishment, Circle of Death, Counterspell, Fireball, Hold Monster, Insect Plague, Magic Missile, Scorching Ray

Multiattack. Zargothrax can make three attacks with his Mace

Mace. Melee Weapon Attack: +18 to hit, reach 10 ft., 1 target. Hit: 20 (3d6 + 10) Bludgeoning damage and the target is pushed up to 5ft away from Zargothrax if it is large or smaller.

Swinging Attack (Recharge 5-6). Zargothrak swings his giant mace in a 10-foot radius semi-circle in front of him. Each creature in that area must make a DC 24 Dexterity Saving Throw, taking 37 (12D6) Bludgeoning damage on a failed save, or half as much on a successful save. On a failed save the creature is also thrown 60 feet back from it's original position and takes an additional 7 (2D6) Falling damage.

Zargothrax has 3 legendary actions. These can only be used at the end of a creature's turn. Zargothrax regains all his legendary actions at the beginning of his turn.

Move (Costs 1 Action). Zargothrax moves up to his movement speed. This movement does not trigger attack of Opportunity.

Unicorn Resurrection (Cost 2 Actions). Zargothrax resurrects any Unicorn within 60ft of him. The Unicorn acts as an ally for Zargothrax. The Unicorn lasts until it's HP are reduced to 0.