Abyss Knight

Abyss Knights are warriors who sneer in the face of suffering, using techniques which injure themselves in order to deliver devastating damage to their opponents.

Features

Dark Burst

Beginning at 3rd level, you are able to weaponize your own life energy to unleash a burst of dark energy against your foes. While under the effect of Darkside, as an action, you may spend 2d4 hit points to cast the Burning Hands spell. When cast in this way, the spell deals necrotic damage instead of fire, and does not ignite flammable objects. Use the Well of Darkness DC when casting the spell.
  You are able to cast the spell at higher levels by increasing the damage you take by 1d4 for each increase in casting level. You may only increase the spell level up to a number of levels equal to your Charisma modifier.

Adversity

Beginning at 6th level, you become fueled by the suffering you endure in battle. For every 20 hit points you are missing, you gain a +1 bonus to attack and damage rolls up to a maximum equal to your Charisma modifier.
    Additionally you gain resistance to necrotic damage.

Supernatural Sense

Beginning at 11th level, you may cast the Detect Good and Evil spell at will. You may also cast Detect Thoughts at will on a willing creature or spend 2 Well of Darkness points to cast it on an unwilling creature.
 

Dark Star

Beginning at 17th level, damage from all sources is reduced by your current Adversity bonus. When you cast Burning Hands using the Dark Burst feature, you deal bonus damage equal to your Charisma Modifier + your Adversity bonus. Additionally, you may change the range from a 15ft. cone to a 30ft. line. You reference the Adversity bonus after spending your hit points to use Dark Burst feature.