Of Denied Nature. The Abyssal Consort can be seen perfectly when within Magical Darkness created by Denied Reality, regardless of how far away it is.  The Abyssal Consort is immune to damage for as long as it is not in direct sunlight.

Shattered Composure. While within direct sunlight or not at its maximum hit points the Abyssal Consort has +2 to AC, +10 ft to its movement speed, but has its attacks weakened.

Flickering Form. The Abyssal Consort's attacks and movement do not provoke opportunity attacks, including those granted by the Sentinel feature.

Legendary Resistance (3/day). 3 times per day if the Abyssal Consort would fail a saving throw, it can choose to succeed instead.

Innate Spellcasting. The Abyssal Consort's innate spellcasting ability is Charisma (Spellsave DC 20).  It can innately cast the following spells:

At will: Phantasmal Force, Silent Image

1/Day each: Black Tentacles, Mental Prison

Abyssal Tar. Upon receiving slashing or piercing from any source or dropping below half its maximum hit points, the Abyssal Consort gains temporary hit points equal to half the damage dealt and creates a Consort’s Spawn in the 5 foot radius around his current space.  This area acts like a cast of the Black Tentacles spell.  Any creatures in this area must succeed a Dexterity Save against the Abyssal Consort’s Spell Save DC or be restrained.

Herald of the Dark. If the Consort has temporary hit points at the start of its turn, it becomes invisible as if under the effects of the Invisibility spell until the start of its next turn.  Any illusions of the Abyssal Consort also appear to go invisible, before reappearing in new locations.

Watcher. The Abyssal Consort marks the target it has most recently damaged.  It can perceive this target as though it has 40 ft of truesight.  If the target leaves this range, the Abyssal Consort can use its reaction to teleport to the last location it perceived the target before they exited its range

Rend Reality (Mythic Trait; Recharges after a Short or Long Rest). If the Abyssal Consort's health would be reduced to 0, it does not die or fall unconscious.  It instead regains half of its hit points and has two illusions that permanently exist.  At initiative count 30, the Abyssal Consort switches positions with one of its illusions unnoticeably.  These illusions otherwise function exactly like the illusions summoned from the Abyssal Consort's _ action.  While this trait is active, the Abyssal Consort's attack actions are no longer weakened by its Shattered Composure trait.

Multiattack. The Abyssal Consort uses Drain Memory.  The Abyssal Consort may then perform two attacks with its Tentacles.  It can replace one of these attacks with its Claws.

Tentacles. Melee Weapon Attack: +8 to hit, reach 30 ft., 1 target. Hit: 15 (2d10 + 3) bludgeoning damage and the target is pulled 10 ft towards the Abyssal Consort and grappled by it.  The Abyssal Consort can have 4 targets grappled this way.  This attack has an additional +3 to hit while the Abyssal Consort's Mythic Trait is active.

Claws. Melee Weapon Attack: +8 to hit, range 5 ft., 1 target. Hit: 17 (4d6 + 3) slashing damage and 7 (2d4 +3) necrotic damage and the target is poisoned.  If the target is already suffering the poisoned condition, they have vulnerability to all damage dealt by this attack.  This poisoned condition ignores immunity to the poisoned condition, but cannot be applied if the target is immune to necrotic damage.  This attack deals an additional 14 (4d4+3) necrotic damage if the Abyssal Consort's Mythic Trait is active.

Drain Memory. The Abyssal Consort looks at its victims and feeds.  One creature within a 30 ft of the Abyssal Consort that can see it must make a DC 12 Constitution saving throw.  If the Abyssal Consort has a marked target, it must use this action on that target.  On a failed save, the target is reduced to 0 hit points as all of their memories are drained from their mind.  If the target is revived from this condition they will have no memory of who they are.  Memories will slowly return over the course of 1d4 weeks after the Abyssal Consort has been killed.  A target reduced to 0 hit points by this action cannot be the target of this action again.  On a successful save the target takes 36 (6d10) necrotic damage.  If the Shattered Composure trait is active but not the Abyssal Consort's Mythic Trait, this action deals 36 (6d10) necrotic damage on a failed save and half as much on a successful one.

Deadly Gallery (Recharge 6).  The Abyssal Consort teleports up to 120 ft away from its current location before summoning 2 illusory duplicates of itself up to 120 ft away from its new location.  A creature can use its action to make an Investigation (Intelligence) check against the Abyssal Consort's spellsave DC to determine if one of these forms are real or fake.  Attacking an illusion allows the Abyssal Consort to use its reaction to teleport within 5 ft of the target and perform its Drain Memory Action on them.

Spread Tar (Recharge 4-6). Up to one Consort's Spawn increases it's radius by 5 ft, up to a maximum of 20 ft.

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

Infect (Costs 1 Action). Each creature suffering from the poisoned condition takes 7 (3d4) necrotic damage.

Sight Unseen (Costs 1 Action). Up to two target creatures with 40 ft. of the Abyssal Consort must make a DC 20 Charisma save or take 7 (3d4) psychic damage and be blinded until the Abyssal Consort's next turn.

Denied Approach (Costs 2 Actions). The Abyssal Consort teleports behind their marked creature.

The Abyssal Consort may use these as Legendary Actions when its Mythic Trait is active.

Restraining Infection (Costs 1 Action). Each marked or poisoned creature within the Abyssal Consort's Lair takes 7 (3d4) necrotic damage and must succeed a DC 20 Constitution Saving Throw or be restrained until the Abyssal Consort's next turn.  Creatures that are both marked and poisoned have disadvantage on the save.

Silent Screech (Costs 1 Action). Each creature within 40 ft. of the Abyssal Consort must succeed a DC 20 Charisma saving throw or take 7 (3d4) psychic damage and be blinded until the Abyssal Consorts next turn.  Marked or poisoned creatures automatically fail this save and take 14 (6d4) psychic damage.

Denial (Costs 2 Actions). The creature marked by the Abyssal Consort must succeed on a DC 22 Charisma Saving Throw or be banished until its next turn.  Upon reappearing they must make this save again, taking 18 (3d10) psychic damage on a failed save as their mind fails to comprehend the maddening horrors they witnessed.