Tasha the Witch

If Tasha fails a saving throw, she can choose to succeed instead.

Tasha has advantage on saving throws against spells and other magical effects. (This trait is bestowed by her Robe of the Archmagi.)

Tasha wears a Robe of the Archmagi.

Tasha makes two Caustic Blast attacks and uses Psychic Whip once.

Melee or Ranged Spell Attack Roll: +14 to hit, reach 5 ft. or range 120 ft., one target. Hit: 21 (6d4 + 6) acid damage.

Tasha psychically lashes out at one creature she can see within 90 feet of herself. The target must make a DC 20 Intelligence saving throw. On a failed save, the target takes 21 (6d6) psychic damage and has the stunned condition until the start of Tasha's next turn. On a successful save, the target takes half as much damage only.

Immediately after Tasha takes damage, she unleashes arcane energy in a 10-foot-radius sphere centered on herself. All other creatures in that area must make a DC 20 Dexterity saving throw, taking 19 (3d12) lightning damage on a failed save or half as much damage on a successful one. Tasha then teleports, along with any equipment she is wearing or carrying, to an unoccupied space she can see within 60 feet of herself.

Tasha casts one of the following spells, using Intelligence as the spellcasting ability (spell save DC 22, +14 to hit with spell attacks):

At will: Detect Magic, Disguise Self, Dispel Magic, Light, Mage Hand, Message, Prestidigitation, Tasha's Hideous Laughter

2/day: Polymorph

1 each/day: Maze, Telekinesis