Spellcasting. The [Zar] is a 20-level spellcaster. Its spellcasting ability is [Intelligence] (spell save DC 24, +10 to hit with spell attacks). The [Zar] has following [All classes] spells prepared:
Cantrips (at will): [Vicious Mockery], [Friends], [Minor Illusion], [Thaumaturgy]
1st level (10 slots): [Charm person], [Command], [Disguise self] 

2nd level( 8 slots): [Suggestion], [Calm emotion], [Zone of truth], [Mirror image] 

3rd level (7 slots):[Enemies abound], [Motivational speech]   

4th level(5 slots):[Charm monster], [dominate beast] 

5th level(5 slots):[Dominate person], [memory modify] , [Seeming]

6th level(5 slots):[Mass suggestion], [Mental prison]

7th level(5 slots):[Power word pain], [Mirage arcane],

8th level(3 slots):[Dominate monster], [Power word stun]

9th level(3 slots):[Psychic scream]

3 actions per turn.

Enchanted whip. Melee Weapon Attack: +11 to hit, reach 10ft., 3 target. Hit: 20 (10d4 + 10) [Slashing] damage. Dc 17 Intelligence saving throw. On a success nothing happens but on a slave he controls the players next 3 turns

Guilt. He urges you to heal him. Dc 20 Intelligence saving throw. On a success you have disadvantage against him. On a failed save they take double the damage he got and Zar regains a half of the health he lost.