Alela, Cunning Conqueror

Magic Resistance. Alela has Advantage on saving throws against spells and other magical effects.

Blessed by Zem'raya. Alela can use up to three reactions, yet may cast spells on only two of them.

Cunning and Ready. Alela has advantage on Initiative and Stealth checks and can't be surprised or ambushed. In her first turn, she is able to cast Greater Invisibility targeting herself as a bonus action.  

Mistress of the Fey. Alela can telepathically control any fey creature she or a projection of her can see, that is on the same plane as her and is CR 4 or lower. The creature acts as if under the effect of Dominate Person or Dominate Beast spell, but only rolls against this effect once it drops bellow 1/3 of its HP. Alela can speak through the creature and the longer it is under her control, the more of its memories she can explore.

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

Evasion. If Alela is subjected to an effect that allows it to make a Dexterity saving throw to take only half damage, the assassin instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.

Ascended Planeswalker. Alela has ascended to the status of a Planeswalker by becoming the champion of the Winter Queen of the Faerie courts. She is able to cast the Planeshift spell once a day without expending a spell slot, any further uses of this ability gives Alela a point of exhaustion. Alela is also able to summon creatures from across realms and planes she has bonded with or dominated, the number and power of said creatures is left to the DM, but any Fae and Water/Air/Forest based elemental is within the realm of the expected. The way the summoning takes place and what resources it requires is left to the Dungeon Master's interpretation. (Deter to Innate Summoning as an alternative)

Multiattack. Alela makes two Ice Claws attacks and can use Crackling Laughter.

Ice Claws. Alela strikes with her nails, infusing them with the bitter cold of the Winter Court. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 17 (3d8 + 5) Piercing damage plus 12 (3d6+6) Cold damage.

Crackling Laughter. Dexterity Saving Throw: DC 22, each creature in a 30-foot Circle around Alela. Failure: 18 (3d12) Lightning damage. Success: Half damage. Failure or Success: The target is cursed until the end of Alela's next turn. The target can't take Reactions until the curse ends.

Innate Summoning. Alela can cast Summon Fae, Conjure Woodland Beings and Conjure Fey twice per day without expending a spell slot.

Spellcasting. Alela is a level 20 spellcaster. Her spellcasting ability is Charisma (spell save DC 22, +12 to hit with spell attacks. Alela has the following spells prepared.

Cantrips (at will): Mind Sliver, Chill Touch, Ray of Frost, Mage Hand, Friends, Minor Illusion, Poison Spray, Message, Frostbite 

1st level (8 slots): Charm Person, Cause Fear, Hex, Puppet, Witch Bolt, Disguise Self, Ray of Sickness, Thunderwave, Silvery Barbs

2nd level (4 slots): Alter Self, Blindness/Deafness, Blur, Crown of Madness, Detect Thoughts, Invisibility, Levitate, Misty Step, Mind Spike, Phantasmal Force, Mirror Image, Suggestion

3rd level (3 slots): Counterspell, Dispel Magic, Antagonize, Fear, Lightning Bolt,Thunder Step, Vampiric Touch, Summon Fae

4th level (3 slots): Charm Monster, Confusion, Dimension Door, Dominate Beast, Greater Invisibility, Ice Storm, Polymorph, Storm Sphere, 

5th level (3 slots): Cone of Cold, Dominate Person, Far Step, Telekinesis, Dream, 

6th level (2 slot): Investiture of Ice, Conjure Fey, Mass Suggestion, Mental Prison, Chain Lightning, Disintegrate

7th level (2 slot): Delayed Blast Fireball, Power Word: Pain, Reverse Gravity, Forcecage

8th level (1 slot): Dominate Monster, Maddening Darkness,  Power Word: Stun, 

9th level (1 slot): Foresight, Power Word: Kill, Mass Polymorph, Time Stop

Sorcerous Talent. Alela can cast a cantrip as a bonus action. She may also cast Invisibility and Misty Step as a bonus action without expending a spell slot.

Ever Nimble. Alela can use the Disengage action as a bonus action and gains additional 15ft of flying speed until end of turn.

Her tricks. Alela casts Counterspell in response to that spell's trigger, using the same spellcasting ability as Spellcasting. If the target fails its saving throw, it is cursed until the end of its next turn. Until the curse ends, the target can't use reactions or bonus actions.

Bend Luck. Subtract 1d4 +1 from a creatures roll.

Spell thief (2/day). Alela tries to steal the magical energy of a spell for her use. If the creature is casting a spell of 2nd level or lower, you automatically steal the spell. You can cast this spell normally without expending a spell slot once within the next 12 hours or until you take a long rest, whichever comes first, after which the stolen spell is lost. To steal a 3rd level spell or higher, you must succeed on your spellcasting ability modifier saving throw with a DC of 10 + the spell's level. Upon success, you steal the spell.

Legendary Reaction (2/day): Counterspell, Silvery Barbs, Misty Escape (without expending spell slots)

Lady's Pride. Alela uses her Ice Claws attack.

Ice and Sparks. Alela casts a cantrip.

Made you look. Alela moves up to 10ft in any direction.