Alien Mind.

If a creature tries to read Belashyrra's thoughts or deals psychic damage to it, that creature must succeed on a DC 22 Intelligence saving throw or be stunned for 1 minute. The stunned creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Eye Thief.

Belashyrra can see through the eyes of all creatures within 120 feet of it. It can use its Eye Ray through any creature within 120 feet of it, as though it were in that creature's space.

Legendary Resistance (3/Day).

If Belashyrra fails a saving throw, it can choose to succeed instead.

Magic Resistance.

Belashyrra has advantage on saving throws against spells and other magical effects.

Regeneration.

Belashyrra regains 20 hit points at the start of its turn. If it takes radiant damage, this trait doesn't function at the start of its next turn. Belashyrra dies only if it starts its turn with 0 hit points and doesn't regenerate.

Teleport.

As a bonus action, Belashyrra can teleport up to 30 feet to an unoccupied space it can see.

Actions

Multiattack.

Belashyrra makes two attacks with its claws and uses its Eye Ray once.

Claw.

Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 17 (3d6 + 7) slashing damage.

Eye Ray.

Belashyrra shoots one of the following magical eye rays of its choice, targeting one creature it can see within 120 feet of it:

1. Psyche-Reconstruction Ray. The target must make a DC 22 Wisdom saving throw, taking 49 (9d10) psychic damage on a failed save, or half as much damage on a successful one. If this damage reduces a creature to 0 hit points, it dies and transforms into a spectator under Belashyrra's control and acts immediately after Belashyrra in the initiative order. The target can't be returned to its original form by any means short of a wish spell.
2. Domination Ray. The target must succeed on a DC 22 Wisdom saving throw or be charmed by Belashyrra for 1 minute or until the target takes damage. Belashyrra can issue telepathic commands to the charmed creature (no action required), which it does its best to obey.
3. Mind-Weakening Ray. The target must succeed on a DC 22 Intelligence saving throw or take 36 (8d8) psychic damage and be unable to cast spells or activate magic items 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. Blinding Ray. The target and each creature within 10 feet of it must succeed on a DC 22 Constitution saving throw or take 19 (3d12) radiant damage and be blinded for 1 minute. Until this blindness ends, Belyshyrra can see through the blinded creature's eyes. The blinded creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Legendary Actions

Belashyrra can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. Belashyrra regains spent legendary actions at the start of its turn.

Claw. Belashyrra makes one claw attack.
Implant Fear (Costs 2 Actions). Belashyrra targets a creature it can see within 60 feet of it. The target must succeed on a DC 22 Wisdom saving throw or take 22 (4d10) psychic damage and immediately use its reaction, if available, to move as far as its speed allows away from Belashyrra.
Rend Reality (Costs 3 Actions). Belashyrra rips at the bonds of reality in its immediate area. Each creature within 10 feet of Belashyrra must succeed on a DC 22 Constitution saving throw or take 19 (3d12) force damage and gain one level of exhaustion.

Lair Actions

While within the Citadel of Lidless Eyes, Belashyrra can invoke the ambient magic to take lair actions. On initiative count 20 (losing initiative ties), Belashyrra can take a lair action to cause one of the following effects; it can't use the same effect two rounds in a row:

An eye opens on a solid surface within 60 feet of Belashyrra. One random eye ray of Belashyrra's shoots from that eye at a target of Belashyrra's choice that it can see. The eye then closes and disappears.
Belashyrra creates a wave of madness. Each creature it can see within its lair must succeed on a DC 22 Wisdom saving throw or be charmed for 1 minute. While charmed in this way, a creature must use its action at the start of its turn before moving to make a melee attack against another creature of Belashyrra's choice within reach. If there are no creatures within reach, the charmed creature can act normally for that turn. A charmed creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Belashyrra taps into the eyesight of creatures in its lair and alters their perception. Each creature of Belashyrra's choice in the lair must make a DC 22 Wisdom saving throw. On a failure, the affected creature perceives objects and creatures a short distance from their actual locations, imposing disadvantage on the creature's attack rolls against those targets. An affected creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to this lair action for the next 24 hours.

Regional Effects

Belashyrra's lair is known to touch remote areas of the Shadow Marches and caverns below Xen'drik. A region containing a passage to Belashyrra's lair is warped by its magic, which creates one or more of the following effects:

Creatures within 1 mile of the passage sometimes feel as if they're being watched.
Beasts that live within 5 miles of the passage undergo magical transmutation, growing eyes or eyestalks that Belashyrra can see through.
A humanoid who spends at least 1 hour within 1 mile of the passage must succeed on a DC 21 Wisdom saving throw or descend into a type of madness (see "Madness of Belashyrra" below). A creature that succeeds on this saving throw can't be affected by this regional effect again for 24 hours.

If Belashyrra dies, these effects fade over the course of 1d10 days.