Cytopathic Reanimation (1/Day).
When Onoma is reduced to 0 hit points, he can attempt to reanimate using his corrupted energy. He makes a DC 10 Constitution saving throw. On a success, he regains half of his maximum hit points (131 HP) and rises again. After reviving, he cannot take any actions until the start of his next turn, during which time his regeneration is active.

Regeneration.
Onoma regains 20 hit points at the start of his turn if he has at least 1 hit point remaining. This regeneration does not restore damage from traumatic brain injuries or psychic damage. If Onoma takes radiant or psychic damage, this trait doesn’t function at the start of his next turn.

Dark Form (Corrupted Form).
Onoma's body is infused with corruption and dark energy, giving him a dark form as a manifestation of his taint. He can switch to his Dark Form once per day, which lasts for 10 minutes. While in Dark Form, Onoma’s AC increases to 20, he gains advantage on all attack rolls, and his movement speed increases by 20 feet. While in this form, Onoma’s regeneration increases to 40 hit points per turn. However, when the form ends, Onoma takes 50 damage and cannot use his regeneration for 1 minute.

Corrupted Flesh.
Onoma’s body constantly secretes a bio-acid that corrodes organic materials. Any creature that grapples or touches Onoma takes 14 (4d6) acid damage at the start of its turn. Onoma is immune to his own bio-acid.

Spellcasting. Onoma is a 12th-level spellcaster. His spellcasting ability is Charisma (spell save DC 17, +9 to hit with spell attacks). Onoma has following Sorcerer spells prepared:

Cantrips (at will): Eldritch Blast, Chill Touch, Thaumaturgy 
1st level (4 slots): Shield, Mage Armor, Ray of Sickness 
2nd level (3 slots): Darkness, Misty Step, Hold Person
3rd level (3 slots): Counterspell, Vampiric Touch, Fear
4th level (3 slots): Blight, Greater Invisibility
5th level (2 slots): Cloudkill, Dominate Person

Corruption Aura.
At the start of each of Onoma's turns, each creature within 10 feet of him must make a DC 18 Constitution saving throw, taking 14 (4d6) necrotic damage on a failed save, or half as much on a successful one. This damage ignores resistance to necrotic damage.

Multiattack.
Onoma makes two attacks with his Dark Energy Manifestations.

Dark Energy Manifestation (Melee or Ranged Weapon Attack):
+12 to hit, reach 15 ft. or range 60 ft., one target.
Hit: 24 (4d8 + 7) force damage. On a hit, the target must succeed on a DC 18 Strength saving throw or be knocked prone.

Dark Energy Blast (Recharge 5-6).
Onoma releases a powerful burst of dark energy in a 30-foot cone. Each creature in that area must make a DC 18 Dexterity saving throw, taking 45 (10d8) force damage on a failed save, or half as much on a successful one. On a failed save, the creature is also stunned until the end of its next turn.

Dark Curse (Recharge 5-6).
Onoma targets a creature within 30 feet and rolls a d4 to inflict a random curse. The target must succeed on a DC 18 Charisma saving throw or suffer the curse for 1 minute. On a critical miss, the curse affects both Onoma and the target. If the target succeeds, they are immune to the curse for 24 hours. The curses are as follows:

1. Curse of Silence: The target is unable to speak or cast spells with verbal components.
2. Curse of Identity: The target loses its sense of identity, becoming unsure of its abilities (disadvantage on saving throws and attack rolls).
3. Curse of Weakness: The target’s Strength and Dexterity scores are halved.
4. Curse of Madness: The target attacks the nearest creature, friend or foe, during each of its turns.

Flight (Bonus Action).
Onoma propels himself into the air with bursts of dark energy, allowing him to fly at a speed of 60 feet. He can use this to gain altitude or avoid attacks, though he cannot maintain flight for more than 10 minutes without landing.

Curse Augmentation.
Onoma chooses a creature within 30 feet that is currently affected by his Dark Curse ability. The curse intensifies, causing the target to take an additional 2d6 necrotic damage at the start of its turn for the next 3 turns.

Shadow Step.
Onoma teleports up to 30 feet to an unoccupied space that he can see within an area of dim light or darkness. Until the end of his next turn, he gains advantage on the first attack he makes after using this ability.

Power Drain (Recharge 5–6).
When Onoma is targeted by a magical attack (spell or magical effect), he can use his reaction to create a dark barrier that absorbs the incoming magic. The barrier can absorb up to 50 points of damage. If the barrier absorbs the full damage of the spell, Onoma takes no damage from the spell. If the spell exceeds the barrier’s damage threshold, Onoma takes the remaining damage after the barrier is shattered. Onoma can only use this reaction once per turn, and the barrier shatters if it absorbs 50 or more points of damage.

Onoma can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature’s turn. Onoma regains spent legendary actions at the start of his turn.

• Dark Energy Strike. Onoma makes one Dark Energy Manifestation attack.
• Corruption Spread. Onoma shoots off traces of corruption, spreading bio-acid in a 20-foot radius around him. Creatures that start their turn in the area must make a DC 18 Constitution saving throw or take 21 (6d6) acid damage.
• Induce Corruption. Onoma targets one creature within 60 feet, attempting to corrupt their mind. The creature must succeed on a DC 18 Wisdom saving throw or become charmed by Onoma for 1 minute, turning into a violent and corrupt version of itself. At the end of each of its turns, the creature can repeat the saving throw.