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

Antimagic Cone. The beholder's central eye creates an area of antimagic, as in the antimagic field spell, in a 150-foot-cone. At the start of each of its turns, the beholder decides which way the cone faces and whether the cone is active. The area works against the beholder's own eye rays,  but not against his artificer spells and abilities. 

Hyper Awareness: Zorgs paranoia gives him advantage, and +3 on all initiative rolls. 

Focused ray: Zorg magnifies the power of one of his eye Ray's, increasing the DC by +4. Or increasing the potency of its effect in some way. Like dealing more damage for one example. He may only do this on one eye ray that uses his action, and one eye ray that uses a legendary action each round. 

Initiative Count: 19.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 14 (4d6) piercing damage.

Eye Rays. The beholder shoots three of the following magical eye rays at random (reroll duplicates), choosing one to three targets it can see within 120 feet of it:

1. Domination Ray. The targeted creature must succeed on a DC 16 Wisdom saving throw or be [Tooltip Not Found] by the beholder for 1 hour, or until the beholder harms the creature.

2. Paralyzing Ray. The targeted creature must succeed on a DC 16 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

3. Fear Ray. The targeted creature must succeed on a DC 16 Wisdom saving throw or be frightened for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

4. Slowing Ray. The targeted creature must succeed on a DC 16 Dexterity saving throw. On a failed save, the target’s speed is halved for 1 minute. In addition, the creature can’t take reactions, and it can take either an action or a bonus action on its turn, not both. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

5. Enervation Ray. The targeted creature must make a DC 16 Constitution saving throw, taking 36 (8d8) necrotic damage on a failed save, or half as much damage on a successful one.

6. Telekinetic Ray. If the target is a creature, it must succeed on a DC 16 Strength saving throw or the beholder moves it up to 30 feet in any direction. It is restrained by the ray’s telekinetic grip until the start of the beholder’s next turn or until the beholder is incapacitated.

If the target is an object weighing 300 pounds or less that isn’t being worn or carried, it is moved up to 30 feet in any direction. The beholder can also exert fine control on objects with this ray, such as manipulating a simple tool or opening a door or a container.

7. Sleep Ray. The targeted creature must succeed on a DC 16 Wisdom saving throw or fall asleep and remain unconscious for 1 minute. The target awakens if it takes damage or another creature takes an action to wake it. This ray has no effect on constructs and undead.

8. Petrification Ray. The targeted creature must make a DC 16 Dexterity saving throw. On a failed save, the creature begins to turn to stone and is restrained. It must repeat the saving throw at the end of its next turn. On a success, the effect ends. On a failure, the creature is petrified until freed by the greater restoration spell or other magic.

9. Disintegration Ray. If the target is a creature, it must succeed on a DC 16 Dexterity saving throw or take 45 (10d8) force damage. If this damage reduces the creature to 0 hit points, its body becomes a pile of fine gray dust.

If the target is a Large or smaller nonmagical object or creation of magical force, it is disintegrated without a saving throw. If the target is a Huge or larger object or creation of magical force, this ray disintegrates a 10-foot cube of it.

10. Death Ray. The targeted creature must succeed on a DC 16 Dexterity saving throw or take 55 (10d10) necrotic damage. The target dies if the ray reduces it to 0 hit points.

BONUS ACTIONS

Invisibility: Casts the invisibility spell on itself.

Radiant Blast: Auto hit, range 60 feet 17 (2d12 + 5) radiant damage. Cannon shit. 

Anti-magic Ray: Zorg magnifies the power of his antimagic cone onto a single opponent. Destroying a single spell slot of a level equal to 1d4, or lower. Using this ability negates the effects of his anti-magic cone until the beginning of his next turn. 

Rocket Barrage: When a creature moves within 20 feet of the beholder it may fire a barrage of rockets at them, forcing them to make a dexteirty saving throw. dealing 4d8 fire damage, and 4d8 force damage. Half on success

Defensive Barrier: When a creature makes a successful attack against Zorg, or causes him to make a dexterity saving throw he may increase its AC, and dexterity saving throws by +4 until the beginning of his next turn. 

The beholder can take 3 legendary actions, using the Eye Ray option below. It can take only one legendary action at a time and only at the end of another creature’s turn. The beholder regains spent legendary actions at the start of its turn.

Eye Ray. The beholder uses one random eye ray.

VILLAIN ACTIONS

Initiative count 22/20 depending on how good PCs roll.

1st round: "BEGONE FROM ME GNAVES! OH WAIT NOT YOU GUYS, GET IN HERE GANG OF BOSSES": All hostile creatures within 30 feet of Zorg are pushed 40 feet away, while 2 regular duergar arrive to join Zorg in the fight. 

2nd: "Is that all you have?!": Zorg heals himself for 40ish points of damage. Or all points of damage. I'm the boss here.

3rd: "Face my Eyeholes!": Zorg shoots eye beams that he hasn't shot yet. Fear, Telekinetic, Death.