Erratic Mutagens. In his pursuit of power, Aackron has consumed hundreds upon hundreds of mutagens, causing multiple to exist in his body simultaneously. Corrupt alchemy has altered his body beyond repair, causing him to always be under the effect of two mutagens from the Blood Hunter's Order of the Mutant mutagen list. These two mutagens shift at the end of his turn. Aackron is considered to be Level 18 for the sake of having access to every single mutagen and having them all at their maximum potency.

Shifting Rites. In addition to his constantly changing mutagens, Aackron has used forbidden techniques to allow him unlimited access to Crimson Rites. Aackron has access to all six Blood Hunter rites and can shift between them at a moment's notice as a bonus action without taking the necrotic damage normally received from invoking a rite. The rite's provide a bonus of 1d10 damage of the associated damage type.

Magic Weapons. Aackron's blade, the Extorter, is magical.

Sinister Augmentation. Through his unyielding devotion to blood, Aackron has gained an uncanny amount of resilience that far surpasses a human's natural ability. He possesses a bonus +5 to all Constitution, Strength, and Dexterity saving throws.

Iron Soul. Due to his vast experience, Aackron is more than capable of facing off against anything and standing in the face of danger. Aackron has advantage on saving throws against being charmed, frightened, paralyzed, stunned, or petrified.

Heretical Spellcasting. Aackron has gone to great lengths to ensure that he has as much power as he could possibly attain. As such, he has found a way to access spells despite not following the Order of the Profane Soul. He has become his own patron for his magic, creating a twisted method of spellcasting that involves using a vial of dragon's blood. The vial contains 10 charges, with charges being consumed depending on the spell cast. Rite Blasts and Crimson Onslaught cannot be used once the vial is fully consumed or stolen, despite not having a cost. Aackron's spellcasting ability is Intelligence (spell save DC 17). 

1 charge: magic missile, thunderwave, misty step

3 charges: Rime's binding ice, burning hands [2nd], chromatic orb [2nd, only lightning variant]

Multiattack. Aackron makes three attacks: two with his sword, the Extorter, and one Rite Blast attack.

Extorter Slash. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 9 (1d8 + 5) slashing damage.

Extorter Thrust. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 8 (1d6 + 5) piercing damage.

Rite Blast. Ranged Spell Attack: +7 to hit, range 120 ft., one target. Hit: 6 (2d6) damage (damage type determined by currently active Rite).

Crimson Onslaught (1/day). Can only be used when Aackron is below half of his maximum hit points. Aackron sends six blades, all manifesting in the form of all of his Rites, and slashes them down in a 5 by 15 foot line in front of him. Each creature within range must succeed on a DC 17 Dexterity saving throw or take 1d10 fire + 1d10 ice + 1d10 lightning + 1d10 necrotic + 1d10 psychic + 1d10 thunder damage, taking half damage on a successful saving throw.

Blood Curse of Binding. Aackron sends out tendrils of blood towards a creature he sees within 30 feet of him. They must make a Strength saving throw (DC 17). If they fail, then they cannot use reactions and their speed is reduced to 0 for one minute. The creature can repeat the saving throw at the end of each of its turns, ending the curse if it succeeds. (2/day)

Blood Curse of the Marked. Aackron clenches his blade and points it towards a creature he sees within 30 feet of him, marking them. Until the end of his turn, attacks against the marked target have advantage and deal an additional 1d10 damage of the damage type of his currently active rite. (2/day)

Blood Curse of Corrosion. Aackron belches onto his blade and points it at a creature he can see within 30 feet of him, causing the vomit to evaporate and transmute a poison into the target creature. They take 4d6 necrotic damage and become poisoned. The target can end the poison if they succeed on a Constitution saving throw (DC 17) at the end of their turn, repeating the saving throw every turn until they succeed. (1/day)

Sanguine Extraction. After landing a melee weapon attack with his Extorter, Aackron can use a bonus action to deal an additional 1d8 necrotic damage by digging the blade deeper into his target, healing for double the necrotic damage dealt with this feature. He can only use this if this is his first attack, and if he does this, it consumes his Multiattack, preventing him from attacking further that turn.

Blood Barrier. Aackron's signature blood spell, the Blood Barrier is a variation of the shield spell that Aackron has designed to protect him against all manner of attacks. It costs 2 charges of the dragon's blood vial to use, shrouding him in a crimson red sphere that wards off all manner of attacks. He can only use this as a reaction to being targeted by any effect. When the barrier is activated, Aackron's AC is increased by 6 and he gains advantage on all saving throws until the end of his next turn.

Aackron can take 2 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. Aackron regains spent legendary actions at the start of its turn.

Extorter Attack. Aackron makes one slash or thrust attack with his Extorter.

Blood Surge (Costs 2 Actions). Aackron opens up his vial of dragon's blood and drinks a sip, regaining 10 (2d10) hit points at the cost of 1 charge of his dragon's blood vial.

Empowered Rite Blast (Costs 2 Actions). Aackron makes one Rite Blast attack that deals 3d6 instead of 2d6 damage.