Aghouri, Demon Prince of Time

Decaying Aura. At the start of each of Aghouri’s turns, each creature with 30 feet of him is aged by 7 (2d6) years. If the creature is immortal, it instead takes 11 (1d20) necrotic damage. If a non immortal creature takes necrotic damage with 20 feet of Aghouri it is aged by an amount of years equal to the damage it took.

Unyielding Essence. Aghouri is immune to any spell or effect that would alter his form, as well as those that would read his thoughts, determine if it he lying, or magically influence his thoughts or behavior.

Sickle of Aghouri. The sickle of Aghouri creates a time bending aura that causes lasting magical effects within 5 feet of it to decay in mere seconds. Lasting magical effects created by artifacts or other non sentient means will regain function once removed from this aura.

Frightful Presence. Each creature of the the abomination's choice that is within 120 feet of the abomination and aware of it must succeed on a DC 16 Wisdom saving throw or become frightened for 1 minute. A 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 the brood spawn's
Frightful Presence for the next 24 hours.

Loyalty. The abomination can instantly teleport to Ustroth at any time.

Legendary Resistance (3/Day). If Aghouri fails a saving throw, he can choose to succeed instead.

Magic Resistance. The abomination has advantage on saving throws
against spells and other magical effects.

Ancient Ritual. If Ustroth is killed, five abominations can sacrifice themselves in a 5 day long ritual to bring him back from the Far Realm yet again. If the ritual is interrupted the abominations die immediately.

Break Resolve. The abomination chooses one target it can see. The target takes 10 (2d6+4) psychic damage and becomes vulnerable to a form of damage that the abomination chooses for 1 round, ignoring resistances and immunities.

Vengeful Shriek. The abomination lets out an ear piercing shriek of pure, raw, hate. All enemy creatures who hear it must made a DC 18 Constitution saving throw or suffer from blindness and deafness for 3 rounds. Magic of divine origin becomes useless for 1 minute in a 30 foot radius.

Cleanse. The abomination chooses a creature it can see within 15 ft and removes up to two negative effects and heals 5 hit points.

Telekinetic Blast. The abomination chooses a creature it can see and throw it 5 ft in any direction. Dealing 42 (4d20) force damage. The target must make a DC 16 Strength saving throw or be knocked prone for 2 rounds.

Negative Energy Ray. Ranged Weapon Attack: +15 to hit, range 50 ft., 1 target. Hit: The abomination drains 1.5 (1d4-1) legendary action from the creature it hits. Negative actions are subtracted from the next time the creature gets legendary actions. If the creature is not legendary it takes 22 (4d8+4) necrotic damage.

Last Breath. The abomination can sacrifice itself to prevent Ustroth from being affected by the action of another creature.

The abomination 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 mind shard regains spent legendary actions at the start of its turn.

Claw Slash (Costs 1 Actions). Melee Weapon Attack: +14 to hit, reach 5 ft., 1 target. Hit: 18 (4d8) magical slashing damage.

Bite (Costs 1 Actions). Melee Weapon Attack: +14 to hit, reach 5 ft., 1 target. Hit:  10 (4d4) magical piercing damage. If the target fails a DC 19 Strength saving throw they are grappled. The target takes 16 (4d6) magical piercing damage if they start their turn while grappled. The target can retry the saving throw as an action.