Cackling Agata the Fate Hag

Bargainer's Folly. If a creature is indebted to Agata on account of a bargain, Agata does not need to concentrate on spells that solely affect that creature. Additionally, the creature has disadvantage on any saves vs a spell or effect which would cause it to be charmed by Agata.

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

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

Innate Spellcasting. Agata can innately cast the following spells, requiring no material components:

At Will: Chill Touch, Frostbite, Prestidigitation, Toll the Dead

Lvl.1 (6 slots): False Life, Hex, Shield, Ray of Sickness

Lvl.2 (5 slots): Blur, Invisibility, Misty Step, Scorching Ray, Delay (see Reactions)

Lvl.3 (4 slots): Bestow Curse, Counterspell, Dispel Magic, Slow, Vampiric Touch

Lvl.4 (3 slots): Banishment, Blight,  Polymorph, Time Skip (see Reactions)

Lvl.5 (3 slots): Cone of Cold, Dominate Person

Lvl.6 (3 slots): Circle of Death, Eyebite, Soul Cage

Lvl.7 (3 slots): Power Word Pain, Finger of Death, Deja Vu (see Reactions)

Lvl.8 (3 slots): Dominate Monster, Power Word Stun Rewind (see Reactions)

Lvl.9 (3 slots): Foresight, Power Word Kill, Time Stop

Multi-Attack. Agata makes three attacks, one with her bite and two with her claws, and uses her Fey's Horror ability.

Claw. Melee Weapon Attack: + 14 to hit, reach 5 ft., 1 target. Hit: 11 (1d8 + 6) slashing damage plus plus 14 (4d6) poison damage.

Bite. Melee Weapon Attack: +14 to hit, range 5 ft., 1 target. Hit: 23 (3d10 + 6) piercing damage plus 14 (4d6) poison damage. The creature must also make a DC 15 Constitution saving throw or be poisoned until the end of its next turn.

Fey's Horror. Agata assumes a horrendous form. Each creature within 60ft of her must succeed on a DC 18 Wisdom saving throw or be frightened of her. The creature may reroll the saving throw at the end of each of its turns, ending the effect on a success. Once a creature succeeds on the saving throw, it is immune to this effect for the next 24 hours.

Time Skip. When Agata is hit by a spell or attack, she can use her reaction and a Level 4 spell slot to cause the attacker to skip 1d4-1 rounds (on a 1, the spell fails) into the future. When this happens, the attacker blinks out of existence for that many rounds and does not apply the effects of its hit until it returns. The attacker will reappear in the location it disappeared, and the fate will not suffer the effects of its hit upon return if she has moved out of range.

Deja Vu. As a reaction when a target Agata can see suffers an effect, the Fate Hag may use a Level 7 spell slot. The target must succeed a CHA save (DC 19) or suffer that effect again at the beginning of their next turn, as well as suffer an additional 2d8 psychic damage.

Rewind. When Agata is a target of an attack, spell, or effect that might harm them (including areas of effect), or fail a roll, the Fate Hag may use her reaction and an 8th level spell slot to immediately undo any effects of that turn. Initiative order jumps back to the beginning of whosever turn it is, and they must succeed a CHA save (DC 19) or be stunned until the beginning of their next turn.

The hag can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The hag regains spent legendary actions at the start of its turn.

Claws. Agata makes one claw attack at a target within range.

Move. Agata moves up to her speed without provoking opportunity attacks.

Cantrip. The Mother Hag can cast one cantrip. 

Cast a Spell (Costs 2 Actions). The Mother Hag casts a spell of 5th level or lower from her spell list that takes 1 action to cast.

Agata's Curse (Costs 3 Actions). Agata chooses one creature within sight of her. The creature suffers 3d10 necrotic damage and Agata regains hit points equal to that amount.