Self Annihilator

You have a made a vow with your blade, turning it from a measly weapon into something greater. Imbue your blade with memories and your life, allowing for more combat power. You learn to fight with your scabbard as your vow commands. The power imbued within your sword is deadly, not just to your enemies, but to yourself as well. You drain your own hp as you attack to gain more power in combat.

The curse of IX

The shadow of Nihility covers the stars equally, and self-annihilators may form in any world. If we call them phenomena, these poor souls do share one thing in common: Their various existential properties — such as corporeal body, mental cognition and personal memories — will gradually fade away in their journey of self-annihilation.

Sacrificial Power

But power comes at a cost. Each strike you deliver exacts a toll upon your own life force. With every swing, you bleed a little more, offering your vitality to fuel the blade’s insatiable hunger. The wounds you inflict upon your enemies mirror the wounds you inflict upon yourself.

Unrelenting Edge

You wield your sword with purpose, no longer arrogant and brash. Unsheathing your sword immediately drains quarter of your current hit points, rounded up. Every attack you make with the unsheathed sword will drain 5% of your hit points rounded down. Defeating an enemy will restore 20% of your maximum hit points. Among these features, each attack with the unsheathed sword will deal 1d12 damage of your choice.  However, every attack with a sheathed sword will deal a fixed 8 bludgeoning damage.

Additionally, you gain the bonus action "Locked In" -

The "Locked In" Bonus Action grants advantage on all melee attacks for 1 minute.

Sin thirster

While your sword is unsheathed, if you are felled in battle you may automatically succeed 1 death saving throw. As a self annihilator, you cannot taste, nor smell.

Quadrivelant Ascendance

When you first unsheathe your sword or an enemy provokes an opportunity attack you may expend a charge to trigger quadrivelant ascendance, dealing 5d12 damage in a 45 foot cone. You have charges equal to half of your proficiency modifier rounded down. These charges reset every long rest.

Apocalypse, The Emancipator

When you activate this ability, your body turns a pale white and only your pupils retain their color. While this happens, red streaks flow across your skin, converging on a point in your body, decided by you.

Effects

• gain 30ft of movement 
• Advantage on dex saves and checks.
• create a 45ft stagnant zone where everyone who enters who is not under the Aeons gaze effect has their speed reduced by 10 and all movement within it is considered difficult terrain.
• Anyone who’s not under the Aeons gaze effect AND is in the zone has disadvantage on constitution checks and saves, and disadvantage on dexterity checks and saves.
• When the ability is ended either by sheathing your weapon or choosing to end it, gain one point of exhaustion.

When you reach level 15, every time you deal damage on a target with crimson drop or detonate a crimson drop, ignore resistance and immunities for the damage.

When you unlock the Horizon Of Existence feature, expand the range to the size of the teleport effect of the feature, and every effect of this feature applies during Horizon Of Existence.

 

Slashed Dreams Cries in Red

Now harnessing the power of the river of pain, Acheron, you now have the ability to remotely inflict pain on enemies. Upon hitting a target you may choose to drain a charge and mark them, dealing 3d4 necrotic. After at least one entity has been marked, you may use a bonus action or action to detonate the marks, removing them and dealing 2d12+5 necrotic damage to each target that had the mark detonated. 
When reaching level 18, increase damage to 3d12.

Horizon of Existence

The Aeon of Nihility, the sleeping and shapeless, IX, The All Consuming Black Hole, all names for THEM, an entity that only believes that the universe is worthless. The embodiment of Nihility. Using this feature creates a plane of existence and drags all targets within 120 feet into the horizon of Nihility, bringing all targets in front of THEM. All targets (except the user and other targets of the users choice) will instantly be struck with unimaginable despair, dropping to their knees, no matter how powerful the entity. The targets struck will immediately drop all weapons, fall to their knees and will be paralyzed until the use commands or until the plane is shattered. When the plane is shattered, all targets that were paralyzed will become unconscious, even when they can’t be put unconscious. All targets that are struck by the user deal an additional 3d12 damage and are guaranteed. During the duration, you may choose to sever their connection to their “path” removing the ability to cast spells for 1d4 days. This plane will last 10 rounds and when it is shattered by the user via their own will, it will deal 8d20 damage. All spells cast in the plane will be sucked into the black hole (the black hole is The Horizon of Existence).