Zyrashka the Sixfold Bladedancer

Aura of Celerity. Creatures within 30 feet of Zyrashka have disadvantage on Dexterity saving throws.

Multi-Armed Mastery. Zyrashka cannot be disarmed of her swords and can interact with up to six objects on her turn. She has advantage on checks and saves to resist being grappled or restrained.

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

Magic Weapons. Zyrashka’s weapon attacks are magical.

Actions

Multiattack. Zyrashka makes six longsword attacks, potentially replacing one with a Tail attack.

Longsword. Melee Weapon Attack: +14 to hit, reach 10 ft., one target.
Hit: 15 (2d8 + 6) slashing damage plus 10 (3d6) psychic damage.

Tail. Melee Weapon Attack: +14 to hit, reach 10 ft., one target.
Hit: 13 (2d6 + 6) bludgeoning damage, and the target is grappled (escape DC 23). Until the grapple ends, the target is restrained, and Zyrashka can’t use her tail on another target.

Flash Step (Recharge 5–6). Zyrashka teleports up to 120 feet to an unoccupied space she can see and makes three sword attacks with advantage.

Reactions

Swordmaster’s Reprisal. When a creature misses Zyrashka with a melee attack, she makes one longsword attack against that creature.

Parry. Zyrashka adds +6 to her AC against one melee attack that would hit her.

Zyrashka can take 3 legendary actions, choosing from the options below. Only one option can be used at a time and only at the end of another creature’s turn.

Quick Strike. Zyrashka makes one longsword attack.
Tail Lash. Zyrashka makes one tail attack.
Whirl of Steel (Costs 2 Actions). Each creature within 10 feet must make a DC 22 Dex save, taking 14 (4d6) slashing on a failed save, or half as much on a success.

When Zyrashka is reduced to 0 hit points, she explodes into shadow and mist, then reforms at 195 hit points in an unoccupied space she can see. All conditions and effects on her end.

If the party is aware of this trait, they gain 62,000 XP for defeating her twice (124,000 XP total).

Zyrashka gets 3 mythic actions, which can only be used while she has her mythic trait active. She regains all expended mythic actions at start of her next turn:

Hasted Strike. Zyrashka makes one longsword attack.
Shadow Step. Zyrashka teleports up to 60 ft.
Storm of Blades (Costs 2 Actions). She moves up to half her speed without provoking opportunity attacks and makes up to three longsword attacks at any points along the movement.
Blade Storm (Costs 3 Actions). Recharge 6.
All enemies Zyrashka can see within 30 feet make a DC 22 Dex save or take
63 (14d8) slashing damage.