Aiden Miller, the Dread Surgeon

Grim Harvest. Whenever Aiden kills a creature or creatures with a spell of 1st or higher level, he regains hit points equal to twice the spell's level or three times its level if the spell came from the School of Necromancy. He does not gain this benefit for killing constructs or undead.

Inescapable Destruction. Necrotic damage dealt ignores resistances to necrotic damage.

Inured to Undeath: Aiden resistance to necrotic damage, and your hit point maximum can't be reduced.

Magic Immunity. Aiden automatically succeeds any saving throw against a spell that targets him and takes no damage from such effects.

Spellcasting. Aiden is an 20th-level spellcaster and a 20th-level cleric. His arcane spellcasting ability is Intelligence (spell save DC 24, +16 to hit with spell attacks), and his clerical spellcasting ability is Wisdom (spell save DC 25, +17 to hit with spell attacks) . Aiden can cast bestow curse and remove curse at will and has the following wizard spells prepared:

Cantrips (at will): dancing lights, fire bolt, light, mending, shocking grasp

1st level (4 slots): detect magic, earth tremor, false life, inflict wounds, magic missile, ray of sickness

2nd level (3 slots): aganazzar's scorcher, blindness / deafness, gentle repose, ray of enfeeblement, silence

3rd level (3 slots): animate dead, counterspell, dispel magic, tongues, revivify

4th level (3 slots): banishment, blight, death ward

5th level (3 slots): antilife shell, cloudkill, hallow, negative energy flood, wall of force

6th level (1 slot): arcane gate, circle of death, create undead, disintegrate, globe of invulnerability

7th level (1 slot): finger of death, power word pain, sequester, teleport, temple of the gods

8th level (1 slot): antimagic field, clone, holy aura

9th level (1 slot): gate

*The archmage casts mind blank, stoneskin and mage armor spells on itself before combat.

Split Focus. Aiden can concentrate on multiple spells at once as long as he is holding his spellbook.

Divine Touch of Death. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 54 (2d8 + 45) necrotic damage.

Antimagic Shock. When a spell effect would damage Aiden, he can disrupt the flow of magic in a 5ft radius around himself as pale green light extends around himself. All magical effects in range come to an immediate end until the end of the turn this ability was used. Magic items or other magic that cannot be dispelled is pushed out of range of this ability.

Antilife Shock. When a living creature would move to a space within 5ft of Aiden, he can cause a barrier of pale blue light to extend from himself. All living creatures within 5ft of Aiden are forced to the nearest space 5ft from him. Creatures cannot enter this range until after the end of the turn this ability was used.

Force Guard. When Aiden is targeted with a physical attack, he can unleash a controlled blast of psychic power to stop the assault. This raises Aiden's AC by 20 for that attack only. Should a melee attack roll be less than Aiden's AC after this increase, Aiden can cause the attacker to become restrained until Aiden's concentration is broken or he uses this ability again. If an attack reacts to with this ability rolls higher than Aiden's modified AC and deals damage, Aiden becomes stunned until the start of his next turn.

Aiden can take 5 legendary actions choosing from the options below. If Aiden is not in possession of his spellbook, he may only take 3 legendary actions. Only one legendary action can be used at a time and only at the end of another creature's turn. Aiden regains all spent legendary actions at the start of his turn.

Cast Spell. Aiden casts a spell of 5th level or lower.

Growing Power. Aiden uses the Growing Power ability of his Grim Grimoire to increase the level of one of his prepared spells by 1.

Library Recall. Aiden uses the Library of Grimoires ability of his Grim Grimoire to prepare a spell from his spell list.