Xavier Hill, Lord of Avernus

Devil's Sight. Magical darkness doesn't impede Xavier's darkvision.

Innate Spellcasting. Xavier's innate spellcasting ability is Charisma (spell save DC 25). He can innately cast the following spells, requiring no material components:
At will: detect magic, alter self
1/day each: chromatic orb, investiture of flame, whirlwind, power word stun, foresight*
*Xavier casts this spell before combat

Spellcasting. Xavier is a 20th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 25, +17 to hit with spell attacks). Xavier has following Warlock spells prepared:
Cantrips (at will): prestidigitation, minor illusion, mage hand, frostbite, fire bolt, acid splash
1st-5th level (4 5th-level slots): armor of agathys*, witch bolt, hellish rebuke, shatter, blur*, thunder step, counterspell, dispel magic, blink, tongues, elemental bane, banishing smite, infernal calling, cone of cold
*Xavier casts this spell before combat

Eldritch Smite. When Xavier hits a creature with his pact weapon, he can expend a 5th level spell slot to deal an extra 27 (6d8) force damage and knock the creature prone.

Lifedrinker. Xavier's attacks made with his pact weapon deals extra necrotic damage equal to his Charisma modifier.

Terra Blade. Xavier's pact weapon is magical. It gives a +3 bonus to attack and damage rolls and does an extra 13 (3d8) damage of either fire, cold, thunder, lightning, or acid (Xavier's choice). Once the damage type is chosen, it cannot be changed for the rest of combat. His pact weapon can be changed into any weapon other than darts, slings, blowguns, hand crossbows, nets, and firearms. The actions below are the prefered weapons Xavier likes to conjure.

Hexblade's Curse. As a bonus action, Xavier curses one creature within 30ft of him for 1 minute. The curse ends early if the target dies, Xavier dies, or Xavier is incapacitated. Until the curse ends, Xavier gains the following benefits:
1. Xavier gains a +8 bonus to damage rolls on the cursed target.
2. Any attack roll on the cursed creature is considered a critical hit on a roll of a 19 or 20.
3. If the cursed target dies, Xavier regains 29 hit points.
When the cursed target dies, Xavier can apply a new curse to another target within 30ft of him.

Accursed Specter. When Xavier kills a humanoid, he can cause a spirit to rise from the corpse using the statistics of a specter. The specter gains 10 temporary hit points and a +9 bonus to attack rolls.

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

Blade of Avernus. Xavier is attuned to the Blade of Avernus, which gives him the following benefits while attuned to this weapon:
1. Xavier gains a +1 to Armor Class.
2. Xavier gains resistance to radiant damage (already applied).
3. Xavier gains immunity to being blinded, deafened, petrified, and stunned.
4. When Xavier rolls a 20 on an attack using this weapon, he lobs off the head of the targeted creature. A creature dies if it cannot survive without the head. 
If Xavier is unattuned to this weapon, he cannot use the Ruler of Avernus and Infernal Recall abilities.

Multiattack. Xavier makes two of the same weapon attack.

Longsword. Melee Weapon Attack: +20 to hit, reach 5 ft., 1 target. Hit:  16 (1d8 + 12) or 17 (1d10 + 12) slashing damage plus 9 necrotic damage plus 13 (3d8) of the chosen damage type.

 Halberd. Melee Weapon Attack: +20 to hit, reach 10 ft., 1 target. Hit: 17 (1d10 + 12) slashing damage plus 9 necrotic damage plus 13 (3d8) of the chosen damage type.

Greataxe. Melee Weapon Attack: +20 to hit, reach 5 ft., 1 target. Hit: 18 (1d12 + 12) slashing damage plus 9 necrotic damage plus 13 (3d8) of the chosen damage type.

Scimitar. Melee Weapon Attack: +20 to hit, reach 5 ft., 1 target. Hit: 15 (1d6 + 12) slashing damage plus 9 necrotic damage plus 13 (3d8) of the chosen damage type.

Longbow. Ranged Weapon Attack: +20 to hit, range 150/600 ft., 1 target. Hit: 16 (1d8 + 12) piercing damage plus 9 necrotic damage plus 13 (3d8) of the chosen damage type.

Breath Weapon (Recharge 5-6). Xavier exhales fire in a 30-foot line that is 5-feet wide. each creature in the line must make a DC 26 Dexterity saving throw or take 17 (5d6) fire damage on a failed save, or half as much on a successful one.

Blade of Avernus. Melee Weapon Attack: +17 to hit, reach 5 ft., 1 target. Hit: 13 (1d8 + 9) slashing damage or 14 (1d10 + 9) slashing damage.

Ruler of Avernus. As an action, Xavier can point the Blade of Avernus at one devil he can see within 60 feet of you. That devil must succeed on a DC 22 Charisma saving throw or be charmed by him for 1 hour. While charmed in this way, the devil follows his orders to the best of its ability. If Xavier commands the devil to do something it perceives as suicidal, the effect ends and he can no longer use this power of the sword against that devil.

Infernal Recall. As an action, Xavier can use the Blade of Avernus to cast word of recall. Creatures transported by this spell appear in an unoccupied space within a sanctuary Xavier designates in Avernus.

Armor of Hexes. If a cursed creature hits Xavier with an attack roll, Xavier can use a reaction to roll a d6. On a 4 or higher, the attack misses regardless of the roll.

Xavier can take 3 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. Xavier regains spent legendary actions at the start of its turn.

Attack (Costs 1 Action). Xavier makes one weapon attack.

Spell (Costs 2 Actions). Xavier casts one spell.