Dread Knight

Those who become known as Dread Knights employ martial skill, techniques, their own rage, bloodlust, and the despair of those around them to enhance their own abilities and devastate their foes and strike fear into the hearts of others. They often instill loyalty through fear, using that fear to manipulate and command others to do as they please, sometimes their might grows to lead others to mistake them as a oathbreaker paladin, blackguard, or even some sort of evil force that maskarades as a mortal man.

Though you can not cast spells proper, you do have various spell like abilities and magical effects 

Charisma is your spellcasting ability for your spell like abilities and magical effects, since you power derives from the strength of your own soul. You use your Charisma whenever a spell like effect or magical effect refers to your spellcasting ability. In addition, you use your Charisma modifier when setting the saving throw DC for a spell like ability or magical effect and when making an attack roll with one.

Spell save DC = 8 + your proficiency bonus + your Charisma modifier

Spell attack modifier = your proficiency bonus + your Charisma modifier

Ravage

Starting at 3rd level, you use your searing hatred and rage to empower your strike with blinding speed and massive force, making the attack even more deadly and likely to hit. Your embracing of your inner darkness has also rendered you immune to emotional manipulation

As a bonus action you can grant yourself a bonus to melee weapon damage rolls equal to your Charisma modifier (minimum of +1).

Dreadful Aspect

Starting at 7th level, you gain resistance to necrotic damage.

Also as an action, you can channel the darkest emotions and focus them into a burst of magical menace. Each creature of the your choice within 30 feet of you must succeed a Wisdom saving throw if it can see you. On a failed save, the target is frightened of you for 1 minute. If a creature frightened by this effect ends its turn more than 30 feet away from you, it can attempt another Wisdom saving throw to end the effect on it.

As a bonus action on your turn, you can give yourself advantage on weapon attack rolls against creatures with the frightened condition until the end of the current turn. When you do so, you also gain temporary hit points equal to your proficiency bonus (PB).

You can use this feature a number of times equal to your PB, and you regain all expended uses of it when you finish a long rest.

Never Ending Hatred

Starting at 10th level, when you roll initiative and have no uses of Ravage remaining, you regain one use.

Your embracing of your inner darkness has also rendered you immune to the frightened and charmed conditions, you also gain proficiency in Charisma saving throws. If you already have this proficiency, you instead gain proficiency in Intelligence or Wisdom saving throws (your choice).

Dauntless Presence

At 15th level, you gain resistance to bludgeoning, piercing, and slashing damage from nonmagical weapons.

Also as a bonus action you can channel the souls of the dead and negative emotions around you to deal necrotic or psychic damage (your choice) when you hit a creature with a melee weapon attack to the target, in addition to the weapon’s damage. The extra damage is equal to your PB + Charisma modifier.

Lord of The Abyss

At 18th level, you can assume a form that reflects your inner darkness, you choose what this form looks like. Using your action, you undergo a transformation. For 1 hour, you gain the following benefits:

•  You surround yourself in a deep shadowy aura that reduces any bright light in a 30-foot radius around you to dim light.

•  An action you Summon forth a weapon made of pure hatred, darkness, or despair, this functions the same as the spell blade of disaster, but the force damage is replaced with necrotic damage. 

• You can cast summon shadowspawn at will, no material components required.

• You can as a bonus action to assert control over another individual by utilizing shadowy apparitions, this effect functions the same as the geas spell, creatures under the frightened condition have disadvantage on this save.

•  If you take damage that reduces you to 0 hit points and doesn’t kill you outright, you can use your reaction to delay falling unconscious, and you can immediately take an extra turn, interrupting the current turn. While you have 0 hit points during that extra turn, taking damage causes death saving throw failures as normal, and three death saving throw failures can still kill you. When the extra turn ends, you fall unconscious if you still have 0 hit points.

After activating this feature, you can't do so again until you finish a long rest.