Abyssal Warrior is a fighter who has to endlessly resist the urge to join the abyss for power.

Sacrifice to The Dark

You give 1d8 of your health to your abyssal weapon to feed it. It grows stronger when you do so. You deal extra damage equal to your proficiency bonus + constitution modifier.

In Touch With The Abyss

You can add an extra proficiency when making any knowledge check about the abyss

Dark Aura

The abyssal energy radiates from you, you gain one of the following:

Life Drain. Flora around you slowly wilts. 

Radius of Unease. Animals with intelligence lower than 4 are extremely uncomfortable around you unless they are also abyssal.

Abyss Fueled Attack

You feed your vitality to your weapon. You take 1d10 damage. You can unleash concantrated beam of abyssal energy from your weapon. It deals double the damage you dealt to the target in the last round.

Once you use this feature you can't use any subclass features until you take a long rest.

Archery

You gain a +2 bonus to attack rolls you make with ranged weapons.

Defense

While you are wearing armor, you gain a +1 bonus to AC.

Dueling

When you are wielding a melee weapon in one hand and no other weapons, you gain a +2 bonus to damage rolls with that weapon.

Great Weapon Fighting

When you roll a 1 or 2 on a damage die for an attack you make with a melee weapon that you are wielding with two hands, you can reroll the die and must use the new roll, even if the new roll is a 1 or a 2. The weapon must have the two-handed or versatile property for you to gain this benefit.

Protection

When a creature you can see attacks a target other than you that is within 5 feet of you, you can use your reaction to impose disadvantage on the attack roll. You must be wielding a shield.

Two-Weapon Fighting

When you engage in two-weapon fighting, you can add your ability modifier to the damage of the second attack.

Tainted Body

Your body gets tainted by your weapon. You are now an abyssal being. You don't eat, sleep but you still need to rest to get your features and hit points back. Also when you are reduced to 0 hit points but not killed outright but you are banished to an unknown realm instead. You may do this once every long rest.

Relentless Hunger

You touch a creature and drain it from it's energy and convert it into abyss energy. You can either drain 1d10 energy as temporary hit points or you can give it an ally but you also give an abyss stack if you have it.

Abyss Master

You have mastered resisting and taming the abyss energy. On your turn as a bonus action you can take control of all the energy in your weapon. Abyss energy and adrenaline flows through your veins. You deal extra 1d8 abyssal damage and give an abyss stack on every attack. And you can use your Abyss Fueled Attack a number equal to your proficiency bonus while in this form.

This form lasts 2 minutes in combat. When combat ends the form ends in 10 seconds.