Voraxium

Absorption Cone. Voraxium has the Magic Resistance trait (advantage on saving throws versus spells and magical effects) while this cone is active. When it succeeds on a saving throw to which Magic Resistance is applied, this cone becomes inactive. The beholder may activate it at the start of each turn. If it does, it gains temporary hit points equal to five times the level of the last spell or effects it resisted (20 if it had no level). Or regain one expended spell slot of the spell level or lower.

Spellcasting. Voraxium is a 15th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 16, +8 to hit with spell attacks). Voraxium has the following wizard spells prepared:

Cantrips (at will): fire bolt, light, mage hand, prestidigitation, minor illusion

1st level (4 slots): detect magic, identify, shield, magic missile, find familiar

2nd level (3 slots): detect thoughts, scorching ray, misty step

3rd level (3 slots): counterspell, haste, melf’s minute meteors

4th level (3 slots): greater invisibility, polymorph, dimension door*

5th level (3 slots): bigby’s hand, scrying, modify memory

6th level (1 slot): disintegrate

7th level (1 slot): reverse gravity

8th level (1 slot): illusory dragon

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

Spellstalks.  Voraxium shoots up to three of the following magical eye rays at one or three creatures it can see within 120 feet of it. It can use each ray only once on a turn.

1. Charm Ray. The targeted creature must succeed on a DC 16 Wisdom saving throw or be charmed  by  Voraxium for 1 hour, or until  Voraxium harms the creature.
2. Paralyzing Ray. The target 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. Lightning Ray: a bolt of lightning arcs toward the target. Three bolts then leap from that target to as many as three other targets, each of which must be within 30 feet of the first target. The targeted creature must succeed on a DC 16 Dexterity saving throw. The target takes 10d8 lightning damage on a failed save, or half as much damage on a successful one.
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. Undead Ray.  This eye allows Voraxium to create undead as in the Create Undead. It operates independently of the time of day and compels the created undead to remain within Voraxium's line of sight.
6. Telekinetic Ray. If the target is a creature, it must succeed on a DC 16 Strength saving throw or Voraxium moves it up to 30 feet in any direction. It is restrained by the ray's telekinetic grip until the start of Voraxium's next turn or until Voraxium 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. Voraxium can also exert fine control on objects with this ray, such as manipulating a simple tool or opening a door or a container.
7. Sensory Ray. The targeted creature must succeed on a DC 16 Constitution saving throw or suffer under the spell Blindness/Deafness  for 1 minute. At the end of each of its turns, the target can make a Constitution saving throw. On a success, the spell ends.
8. Freezing Ray.  This eye allows Voraxium to create a wall of ice as in the Wall of Ice spell.  DC 16
9. Sickening Ray. The targeted creature must succeed on a DC 16 Wisdom saving throw, on a failed save the target has a disadvantage on attack rolls and ability checks. At the end of each of its turns, it can make another Wisdom saving throw. If it succeeds, the effect ends.
10. Dulling Ray.  The targeted creature must succeed on a DC 16 Intelligence saving throw or suffer under the spell Feeblemind.