Carnage

Dark Devotion. Carnage has advantage on saving throws to avoid or end the Charmed or Frightened conditions.

Favored by the Gods (Recharges after a Short or Long Rest). When Carnage fails a saving throw or misses with an attack roll, she can roll 2d4 and add it to the total, possibly changing the outcome.

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

Special Equipment. Carnage wears a pair of bracers of defense, a ring of alter self (functions as a mask of alter self), and she wields a dagger of Hecate.

Spellsense. While holding the Dagger of Hecate, Carnage knows if a creature she can see within 30 feet of her is capable of casting spells, and what the highest level spell it can cast is. In addition, Carnage has advantage on Intelligence (Arcana) checks made to identify spells. 

Multiattack. Carnage makes three Dagger of Hecate attacks. Carnage can replace two attacks with a use of Charm or Spellcasting.

Dagger of Hecate. Melee or Ranged Spell Attack: +12 to hit, reach 5 ft. or range 120 ft., one target. Hit: 28 (4d10 + 6) necrotic or Psychic damage.

Spellcasting. Carnage casts one of the following spells using Charisma as the spellcasting ability (spell save DC 20):

At Will: Alter Self, Detect Magic, Detect Thoughts, Fireball (level 5 version), Invisibility, Mage Armor (cast before combat), Mage Hand, Nystul's Magic Aura (cast before combat), Prestidigitation, Thaumaturgy
2/Day Each: Animate Dead, Blindness/Deafness (level 4 version), Dimension Door, Teleport
1/Day Each: Abi-Dalzim's Horrid Wilting, Chain Lightning, Cone of Cold, Dominate Person (level 8 version), Finger of Death, Power Word Kill, Scrying

Empowered Spell (6/Day). When Carnage rolls damage, she can reroll up to 6 damage dice. She must use the new rolls.

Heightened Spell (3/Day). When Carnage forces a creature to make a saving throw to resist the effects, Carnage gives one target disadvantage on its first saving throw against the spell. 

The Dagger Hungers. The dagger of Hecate has 9 charges. Carnage can expend a charge to give herself Advantage on her next attack roll. The dagger of Hecate regains 1d6 + 3 daily at dawn. 

Unearthly Recovery (Recharges after a Long Rest). When Carnage has fewer than 75 hit points, she regains 75 hit points. 

Hellish Rebuke (3/Day). Carnage casts Hellish Rebuke (level 2 version) in response to the spell's trigger, using the same spellcasting ability as Spellcasting. 

Protective Magic. Carnage casts Counterspell or Shield in response to the spell’s trigger, using the same spellcasting ability as Spellcasting.

Legendary Action Uses: 3. Immediately after another creature’s turn, Carnage can expend a use to take one of the following actions. Carnage regains all expended uses at the start of each of her turns.

Deathly Teleport. Carnage teleports up to 60 feet to an unoccupied space she can see, and each creature within 10 feet of the space she left takes 11 (2d10) Necrotic damage.

Death Bloom. Constitution Saving Throw: DC 20, each creature that isn't a Construct or Undead in a 20-foot Emanation originating from Carnage. Failure: 18 (4d8) Necrotic damage. Success: Half damage. Failure or Success: Carnage regains Hit Points equal to half the total Necrotic damage dealt, and Carnage can’t take this action again until the start of her next turn.

Dreadful Gaze. Carnage casts Fear, using the same spellcasting ability as Spellcasting. Carnage can’t take this action again until the start of her next turn.