Absolute Raven, Dream Fulfilled (wip)

Legendary Resistance (3/Day, or 4/Day in Lair). If the beholder fails a saving throw, it 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.

Swallow: Strength Saving Throw: DC 16, one Large or smaller creature Grappled by the Beholder (it can have up to two creatures swallowed at a time). Failure: The target is swallowed by the beholder, and the Grappled condition ends. A swallowed creature has the Blinded and Restrained conditions, has Total Cover against attacks and other effects. A swallowed creature takes 2d8+7 bludgeoning damage and 2d6 acid damage at the start of their turns. A creature can deal 15 total piercing slashing, force or necrotic damage to a gizzard inside the beholder to break free of the grapple, which causes the beholder to spit them out to the nearest unoccupied space

Bite. Melee Attack Roll: +8, reach 5 ft. Hit: 13 (3d6 + 3) Piercing damage.

Multiattack. The beholder uses Eye Rays three times.

1. Charm Ray. Wisdom Saving Throw: DC 16. Failure: 13 (3d8) Psychic damage, and the target has the Charmed condition for 1 hour or until it takes damage. Success: Half damage only.
2. Paralyzing Ray. Constitution Saving Throw: DC 16. Failure: The target has the Paralyzed condition and repeats the save at the end of each of its turns, ending the effect on itself on a success. After 1 minute, it succeeds automatically.
3. Fear Ray. Wisdom Saving Throw: DC 16. Failure: 14 (4d6) Psychic damage, and the target has the Frightened condition until the end of its next turn. Success: Half damage only.
4. Slowing Ray. Constitution Saving Throw: DC 16. Failure: 18 (4d8) Necrotic damage. Until the end of the target's next turn, the target's Speed is halved; the target can't take Reactions; and it can take either an action or a Bonus Action on its turn, not both. Success: Half damage only.
5. Telekinetic Ray. Strength Saving Throw: DC 16 (the target succeeds automatically if it is Gargantuan). Failure: The beholder moves the target up to 30 feet in any direction. The target has the Restrained condition until the start of the beholder's next turn or until the beholder has the Incapacitated condition. The beholder can also exert fine control on objects with this ray, such as manipulating a tool or opening a door or container.
6. Sleep Ray. Wisdom Saving Throw: DC 16 (the target succeeds automatically if it is a Construct or an Undead). Failure: The target has the Unconscious condition for 1 minute. The condition ends if the target takes damage or a creature within 5 feet of it takes an action to wake it.
7. Petrification Ray. Constitution Saving Throw: DC 16. First Failure: The target has the Restrained condition and repeats the save at the end of its next turn if it is still Restrained, ending the effect on itself on a success. Second Failure: The target has the Petrified condition instead of the Restrained condition.
8. Disintegration Ray. Dexterity Saving Throw: DC 16. Failure: 36 (8d8) Force damage. If the target is a nonmagical object or a creation of magical force, a 10-foot Cube of it disintegrates into dust. Success: Half damage. Failure or Success: If the target is a creature and this damage reduces it to 0 Hit Points, it disintegrates into dust.
9. 7th level Finger of death Ray*. Dexterity Saving Throw: DC 16. Failure: 61 (7d8+30) Necrotic damage. Success: Half damage. Failure or Success: The target dies if the ray reduces it to 0 Hit Points. A humanoid killed by this spell rises at the start of your next turn as a zombie that is permanently under your command, following your verbal orders to the best of its ability.
10. 6th level Chain lightning Ray* DC 16 dexterity saving throw 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. A target can be a creature or an object and can be targeted by only one of the bolts.A target must make a Dexterity saving throw. The target takes 10d8 lightning damage on a failed save, or half as much damage on a successful one.

Dominate Beholder* 9th level (At Will). Wisdom Saving Throw: DC 27, one creature that is a beholder or beholder-kin can see within 30 feet. Failure: The target has the Charmed condition until the Beholder dies. While Charmed, the target acts as a friendly ally to the Beholder and is under its control while within 60 feet of it. In addition, the beholder and the target can communicate telepathically with each other over any distance as long as they're on the same plane. 

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Legendary Action Uses: 3 (4 in Lair). Immediately after another creature’s turn, the aboleth can expend a use to take one of the following actions. The aboleth regains all expended uses at the start of each of its turns.