Corpse Puppeteer

Magic Resistance.  The Corpse Puppeteer has advantage on saving throws against spells and other magical effects.

Magic Weapons.  The Corpse Puppeteer's weapon attacks are magical..

Master of Puppets.  Any zombies under the Corpse Puppeteer's control within 60 feet make attack rolls and saving throws with advantage.  The puppeteer can control up to twenty zombies at any one time.  If the puppeteer dies, any zombies under its control immediately crumble into piles of flesh.

Multiattack.  The puppeteer makes three Withering Ray attacks or two Slam attacks.

Slam. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 38 (6d10 + 5) bludgeoning damage. 

Withering Ray. Ranged Spell Attack: +9 to hit, range 60 ft., one target. Hit: 26 (4d12) necrotic damage.  The target must succeed on a DC17 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken.  This reduction lasts until the target finishes a long rest.  If the target's hit point maximum is reduced to 0, it dies and rises at the start of the puppeteer's next turn as a zombie that is permanently under the puppeteer's command.

Stirring Shriek (Recharges after a Short or Long Rest).  The puppeteer releases a horrific, piercing shriek.  Each other creature that is not undead within 60 feet that can hear the shriek must succeed on a DC17 Wisdom saving throw, taking 28 (8d6) psychic damage and become frightened for 1 minute on a failure.  Then, up to 10 corpses within 60 feet of the puppeteer rise as zombies that are permanantly under the Corpse Puppeteer's command.  A creature can repeat the saving throw at the end of each of it's turns, ending the effect on itself on a success.