Legendary Resistance (3/Long Rest). If Yone fails a saving throw, he can choose to succeed instead.
Azakana's Sight. Yone's darkvision has a range of 120ft. and cannot be impeded by magical darkness (such as the darkness spell). Additionally, he can partly see into the Spirit Realm and can see through illusions made by Azakana.
Way of the Hunter. Yone is a former apostle of the Wind Technique, an ancient sword-style that commands the wind as a deadly tool and wields spirit magic in mask and blade. Yone has the following benefits:

• Intent: Yone critically strikes on a roll of 19-20 on the d20.
• Steel and Spirit: Yone attacks alternate between his Steel Blade and Azakana Blade:
  
  • Mortal Steel: Yone's attacks with his Steel Blade generate a stack of Gathering Storm when they hit, stacking up to 2 times. At 2 stacks, Yone's next attack surrounds him with wind a 15-foot radius.
  • Azakana Blade: Yone's attacks with this blade deal psychic damage and ignore resistance.
• Mobile: Yone has a 10-foot bonus to his walking speed. Additionally, Yone doesn't trigger attacks of opportunity from creatures if he has made an attack against them this turn whether he hits or not.
• If Yone is in combat with an Azakana spirit, when it falls to 25% of it's max hit points he may seal it in a mask by piercing it with his Azakana Blade and speaking it's true name. If Yone has studied the demon for at least 10 minutes prior to combat, he may seal it at half it's max hit points instead.

When Will I Know Peace.. Yone is cursed by the Azakana mask attached to his face. If he dies, his spirit returns to the Spirit Realm of Ionia. After 5 (1d10) days, he returns to the Material Realm fully rejuvenated. Only a Wish, a Cleric's Divine Intervention, or the true name of the Azakana cursing Yone can allow him to pass on permanently.

Multiattack. Yone makes three Steel Tempest or Azakana Blade attacks.

Steel Blade. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 16 (2d8 + 6) piercing damage.
Gathering Storm: All creatures must succeed a DC 17 Strength saving throw or be launched 30ft airborne (12 (3d6)) and take 16 (4d6) thunder damage and land prone. Creatures take half as much damage and are not flung airborne on a success.
Azakana Blade. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 16 (2d8 + 6) psychic damage.
Spirit Cleave. Yone swings his Azakana Blade in a 15-foot radius arc. Creatures of Yone's choice in this arc must succeed a DC 16 Charisma saving throw or take 18 (4d6) psychic damage or half as much on a success. Yone gains temporary hit points equal to the damage dealt.
Fate Sealed (Recharge 5-6). Yone dashes with unseen speed in a 10-foot wide 60-foot long line, stopping after the last target in the line. All creatures of Yone's choice in this area must make a DC 18 Dexterity saving throw. Creatures take 30 (5d10) slashing damage and 30 (5d10) psychic damage and are launched 30ft airborne (12 (3d6)) on a failure. Creatures take half as much damage and are not flung airborne on a success.
If this damage (excluding the 30-foot fall  damage) reduces a creature to 0 hit points, they fall unconscious with 1 death saving throw failure. If this damage reduces an Azakana to 0 hit points they are instantly sealed into a mask.

Second Wind (Recharges after a Short or Long Rest). Yone regains 30 hit points.

Soul Unbound (Recharge 5-6). Yone separates his spirit from his body until initiative 20 (losing ties) on the next round. During this time, Yone's body is immune to all damage. His spirit, magically tethered to his body, gains the following benefits:

• Yone gains an additional 10 walking speed.
• 25% of the total damage Yone deals to creatures is dealt again as psychic damage.
• Yone may make one attack with his Steel or Azakana Blade as a bonus action.
• Yone's spirit form takes half damage from all sources except magical weapons.

Yone 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. Yone regains spent legendary actions at the start of his turn.

One to Cut, One to Seal. Yone makes one attack with Steel Tempest or Azakana Blade.
As the Wind. Yone moves up to half his speed without triggering opportunity attacks.
Kase'ton! (Costs 2 Actions). If Gathering Storm has 2 stacks, Yone uses Steel Blade to strike with the wind.
Carve the Spirit! (Costs 2 Actions). Yone attacks with Spirit Cleave. The temporary hit points gained are halved.
My Blades Know Your Name! (Cost 3 Actions). Yone recharges Fate Sealed.