Antiweapon Cone. Xanathar's central eye creates a 200 foot cone. All weapon attacks in that area have disadvantage. This also creates the effect of an Antimagic Field spell.

Spellcasting. Xanathar is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 22, +14 to hit with spell attacks). Xanathar has the following wizard spells from Xanathar's Guide to Everything prepared:

Cantrips (at will): create bonfire, frostbite, shape water

1st level (4 slots): absorb elements, cause fear, earth tremor

2nd level (3 slots): Aganazzar's scorcher, dragon's breath, dust devil, shadow blade

3rd level (3 slots): catnap, erupting earth, flame arrows, wall of water

4th level (3 slots): elemental bane, sickening radiance, summon greater demon, vitriolic sphere

5th level (3 slots): control winds, dawn, infernal calling

6th level (2 slots): create homunculus, mental prison,

7th level (1 slot): power word pain, whirlwind

8th level (1 slot):  Abi-Dalzim's horrid wilting, illusory dragon

9th level (1 slot): invulnerability, mass polymorph, Host of the House (see my homebrew spells).

Bite. Melee Weapon Attack: +1 to hit, reach 5 ft., one target. Hit: 2 (6d6 − 1) piercing damage.

Eye Rays. The spectator shoots up to 2 of the following magical eye rays at one or two creatures it can see within 90 feet of it. It can use each ray only once on a turn.

1. Confusion Ray. The target must succeed on a DC 16 Wisdom saving throw, or it can’t take reactions until the end of its next turn. On its turn, the target can’t move, and it uses its action to make a melee or ranged attack against a randomly determined creature within range. If the target can’t attack, it does nothing on its turn.
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. Fear Ray. The target must succeed on a DC 17 Wisdom saving throw or be frightened for 1 minute. The target can repeat the saving throw at the end of each of its turns, with disadvantage if the spectator is visible to the target, ending the effect on itself on a success.
4. Wounding Ray. The target must make a DC 17 Constitution saving throw, taking 16 (3d10) necrotic damage on a failed save, or half as much damage on a successful one.

5. Charm Ray. The targeted creature must succeed on a DC 22 Wisdom saving throw or be charmed by Xanathar for 2 hours, or until Xanathar charms another creature.

   Paralyzing Ray. The targeted creature must succeed on a DC 22 Constitution saving throw or be paralyzed for 2 minutes. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

   Fear Ray. The targeted creature must succeed on a DC 22 Wisdom saving throw or be frightened for 2 minutes. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

   Slowing Ray. The targeted creature must succeed on a DC 22 Dexterity saving throw. On a failed save, the target’s speed is halved for 2 minutes. 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.

   Enervation Ray. The targeted creature must make a DC 22 Constitution saving throw, taking 36 (8d10) necrotic damage on a failed save, or half as much damage on a successful one.

   1. Telekinetic Ray. If the target is a creature, it must succeed on a DC 18 Strength saving throw or Xanathar moves it up to 40 ft. in any direction. It is restrained by the ray’s telekinetic grip until the start of Xanathar’s next turn or until Xanathar 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 ft. in any direction. Xanathar can also exert fine control on objects with this ray, such as manipulating a simple tool or opening a door or a container.

   Sleep Ray. The targeted creature must succeed on a DC 22 Wisdom saving throw or fall asleep and remain unconscious for 2 minutes. 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.

   Petrification Ray. The targeted creature must make a DC 22 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.

   Disintegration Ray. If the target is a creature, it must succeed on a DC 18 Dexterity saving throw or take 45 (10d10) 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.

   Death Ray. The targeted creature must succeed on a DC 18 Dexterity saving throw or take 55 (10d12) necrotic damage. The target dies if the ray reduces it to 0 hit points.

Create Food and Water. The spectator magically creates enough food and water to sustain itself for 24 hours.

Can Attack as a bonus action or Use Misty step to move in and out of combat 

Spell Reflection. If the spectator makes a successful saving throw against a spell, or a spell attack misses it, the spectator can choose another creature (including the spellcaster) it can see within 30 feet of it. The spell targets the chosen creature instead of the spectator. If the spell forced a saving throw, the chosen creature makes its own save. If the spell was an attack, the attack roll is rerolled against the chosen creature.

At the end of Xanathar's turn, it takes an extra bonus action to use up to 4 legendary actions.

Eye Ray. Xanathar uses a random eye ray.

Full Heal Ray. Xanathar can heal once every 1 minute 

Lair and Lair Actions