Mutated Regeneration: Yun regains 20 hit points at the start of his turn. He does not regain hit points from radiant damage. If Yun is reduced to 0 hit points, he immediately transforms into a more monstrous form, losing some of his intelligence and gaining new abilities (see "Mutated Transformation").

Unholy Science: Yun can use a bonus action to throw a vial of his alchemical concoctions at a creature within 30 feet. The target must make a DC 17 Constitution saving throw or suffer one of the following effects (Yun’s choice):

• Confusion Vial: The target is confused for 1 minute (as per the confusion spell).
• Flesh Rot Vial: The target takes 14 (4d6) necrotic damage and must make a DC 15 Constitution saving throw or have their movement speed halved for 1 minute.
• Chemical Mutation Vial: The target must make a DC 15 Dexterity saving throw or become poisoned for 1 minute, and during this time, the target can take no reactions.

Bonecraft: As a bonus action, Yun can cause bones and body parts to emerge from his body, manifesting as bone blades or claws that he can use for his attacks. This ability grants him +2 to attack rolls with his claws and bone weapons.

Skeletal Minions (Recharge 5-6): Yun can raise 1d4+1 skeletal minions in a 30-foot radius from the surrounding area (usually bones, corpses, or his own experiments). These skeletal warriors act immediately and fight under Yun’s control. They are animated as per the Animate Dead spell but remain in the fight for as long as Yun chooses, regenerating 5 hit points at the start of each of his turns. They act on their own initiative and can attack once on their turn.

Multiattack: Yun makes two attacks: one with his Bone Blade or Twin Swords, and one with his Claw attack.

Bone Blade (Melee Weapon Attack): +9 to hit, reach 5 ft., one target. Hit: 14 (2d6 + 6) slashing damage, plus 7 (2d6) necrotic damage.

Twin Swords (Melee Weapon Attack): +9 to hit, reach 5 ft., one target. Hit: 12 (2d4 + 6) slashing damage, plus 7 (2d6) necrotic damage.

Claw (Melee Weapon Attack): +7 to hit, reach 5 ft., one target. Hit: 10 (1d8 + 6) slashing damage.

Chemical Concoction (Recharge 5-6): Yun hurls a vial filled with a volatile chemical mixture at a target within 60 feet. The target must make a DC 18 Dexterity saving throw. On a failed save, the target takes 22 (4d10) acid damage and 14 (4d6) necrotic damage. On a successful save, the target takes half damage.

Mutated Transformation (Recharge 5-6): As a last resort, Yun can inject himself with a vial of mutagenic chemicals. This transformation lasts for 1 minute and grants Yun the following benefits:

• +4 to Strength and Dexterity, +2 to Constitution
• Movement speed increases by 20 feet
• Yun’s Intelligence decreases by 2
• He gains an additional action to make a Claw Attack once per turn.

At the end of the transformation, Yun must make a DC 16 Intelligence saving throw. On a failure, he loses 1 point of Intelligence permanently as the chemicals affect his mind. He can repeat the saving throw at the end of each transformation until he succeeds or his Intelligence is reduced to 0.

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

• Bone Strike: Yun makes a Bone Blade or Twin Sword attack.
• Chemical Distraction (Costs 2 Actions): Yun throws a vial of chemical concoction at a creature within 30 feet. The target must make a DC 15 Dexterity saving throw or be affected by one of the following effects (Yun's choice):
  • Flesh Rot Vial or Chemical Mutation Vial
  • Confusion Vial
• Regenerate (Costs 3 Actions): Yun regains 30 hit points.