Special equimpent.   Adromorn wears a robe of eyes that lets him see in all directions, gives him darkvision out to a range of 120 feet, grants advantage on Wisdom (Perception) checks that rely on sight, and allows him to see invisible creatures and objects, as well as into the Ethereal Plane, out to a range of 120 feet.

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

Legendary Resistance (5/Day). If Adromorn fails a saving throw, he can choose to succeed instead.

Plane Orbs. Adromorn has four orbs corresponding to the Outer Planes. When he is drop to 0 hit points he is teleported to one plane of his choice and the corresponding Orb is destroyed. Moreover, he regains all hit points and spell slots used.

Spellcasting. Adromorn is a 25-level spellcaster. Its spellcasting ability is intelligence (spell save DC 26, +19 to hit with spell attacks). He can cast plane shift, gate and banishment at will. Adromorn has studied for thousand of years, he knows all wizards spells:
Cantrips (at will) 
1st level (at will); 2nd level (at will); 3th level(4 slots); 4th level (4 slots); 5th level (4 slots);  6th level (3 slots); 7th level (2 slots); 8th level (2 slots); 9th level (2 slots)

Time touch. Melee Spell Attack: +19 to hit, reach 5 ft., one creature. Hit: 24 (8d6) force damage. The target must succeed on a DC 22 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.

Banishment. If Adromorn is hit by a melee or range attack he can banish the creature to another plane (Charisma save DC 22) until the end of the creature next turn.

Adromorn can take 5 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. Halaster regains spent legendary actions at the start of its turn.

Cast spell. Adromorn casts a spell of 5th level or lower.

Teleport. Adromorn teleports to an unoccupied space he can see within 50 feet of him.

Time touch (Costs 2 Actions). Adromorn uses his time touch.