Allin

The Dark Lord's Terror. Once Allin enters combat, every creature within a 400-foot radius of Allin must make a DC 25 Wisdom saving throw or be frightened for 1 minute.  The target can reroll the save at the start of each of its turns.

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

Magic Weapons. Allin's weapon attacks are magical.

Spell Resistant:  Any spell that Allin is hit by that requires a to-hit roll is reflected back at a target of his choosing.

Multiattack. Allin makes 4 attacks and can cast 1 cantrip.

Darkened Sword. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 23 (2d12 +10) slashing damage plus 9 (2d8) necrotic damage.

Claws: Melee Weapon Attack: +19 to hit, reach 5 ft., one target.  Hit: 36 (4d12+10) bludgeoning damage plus 18 (4d8) fire damage.   

Spells list

Cantrips (At will): Acid Splash, Chill Touch, Eldritch Blast, Fire Bolt, Frostbite, Mage Hand, Mending, Poison Spray, Produce Flame, Ray of Frost, Resistance, Shocking Grasp, Sword Burst, Thaumaturgy, Thorn Whip

1st level (At will):  Absorb Elements, Bane, Burning Hands, Chaos Bolt, Charm Person, Comprehend Languages, Detect Magic, Ray Of Sickness, Guiding Bolt, Hellish Rebuke, Ice Knife.

2nd level (At Will): Blindness/Deafness, Cloud of Daggers, Darkness, Dragon's Breath, Enthrall, Hold Person, Knock, Mind Spike, Misty Step, Detect Thoughts.

3rd level (8 slots): Dispel Magic, Counterspell, Speak With Dead, Fireball, Counterspell, Animate Dead, Blink, Call Lightning, Fly, Lightning Bolt.

4th level (6 slots): Banishment, Black Tentacles, Blight, Greater Invisibility, Ice Storm, Spirit of Death, Storm Sphere, Wall of Fire.

5th level (5 slots): Animate Objects, Cone of Cold, Destructive Wave, Telekinesis, Dominate Person, Maelstorm.

6th level (4 slots): Disintegrate, Circle of Death, Chain Lightning, Mass Suggestion, Primordial Ward, Wall of Ice.

7th level (4 slots): Plane Shift, Power Word Pain, Teleport, Whirlwind.

8th level (3 slots): Dominate Monster, Earthquake, Illusionary Dragon.

9th level (3 slots): Time Stop, Power Word Kill.

Summoning:  Allin can summon 7 (2d6) loyal cultists to fight for him.

Mind Control:  Allin attempts to mind control a creature within 30 feet of him.  The creature must make a DC 18 Wisdom save or be mind-controlled for 1 minute, the creature can reroll its save at the beginning of each of its turns.

Dark Thunder:  Allin creates tremors in the ground, every creature within a 60-foot radius of him must make a DC 18 Dexterity save or be knocked prone till the beginning of its next turn.

Setback:  When Allin is hit with a melee attack, he can use his reaction to bash the target.  The target must make a DC 20 Constitution save or be blinded until the start of its next turn.

Sharp defense:  When Allin is hit with a melee attack, Allin's armor can grow spikes to pierce the target,.  The target must make a DC 20 Dexterity save or take 9 (2d8) piercing damage.

Parry:  Allin can parry an attack, reducing the amount of damage done to him by 13 (2d12) points, and Allin's AC is increased to 28 against the next attack.

Allin can use 1 legendary action per turn.  Choose 1 of the 3 actions below for Allin to use.  Once an action is used, he cannot use the same action until he's had a long rest.

Corrupt Grasp:  Allin releases a dark rupture of corrupting smoke.  Every creature within an 80-foot cone must make a DC 26 Dexterity saving throw.  On a failed save, the creature takes 65 (10d12) points psychic of damage and is blinded for 1 turn, half as much on a successful save.

Darkness Rising:  Allin creates a storm that clouds an area of 400 feet.  Each creature in the radius must make a DC 25 Perception check to see Allin through the fog, each creature that fails has disadvantage on their attack rolls and saving throws while Allin has advantage against the blinded creatures.  Each creature must also make a DC 25 Constitution saving throw at the start of each of its turns.  On 3 failed saves, the creature is turned to stone, and on 3 successful saves the creature isn't affected

Abaddon:  Allin creates a gateway to his realm of Abaddon that lasts for 1 hour or until he wants it to end.

Allin can use 1 mythic action per turn.  Choose 1 of the 2 actions below for Allin to use.  Once an action is used, he cannot use the same action until he's had a long rest.

The Dark Lord's Grimoire:  Allin summons his Grimoire into his hand and draws upon its magic, causing the ground in a 500ft radius around him to darken, and from the darkness arises thousands of shadowy claws.  Every creature within the radius must make a DC 26 strength saving throw.  On a failed save, the creature is grappled by the hands and takes 78 (12d12) points of slashing damage, and on a successful save they resist the grapple and take half as much damage.

The Fruit of Corruption:  Allin summons the dark magic from his realm of Abaddon and regains 130 (20d12) hit points.