Oath of Unforgiveness

Sometimes a paladin is forced to break their oath. When a strong oath is broken that conviction can sometimes manifest in unforgiving rage. This rage is fueled by a holy madness, one so overwhelming it manifests in a calm and calculated manner. Some call those that follow the Unforgiving path Holy Warlocks and some refer to them as Rage Priests.

Channel Divinity

When you take this oath at 3rd level, you gain the following two Channel Divinity options.

Somber Rage. In battle, you fight with holy anger. On Your Turn, you can enter a rage as a Bonus Action. While raging, you gain the following benefits:

You have advantage on Strength Checks and Strength Saving Throws. 
When you make a melee weapon attack using Strength, you gain a +2 bonus to the damage roll. This bonus increases as you level.
You have Resistance to bludgeoning, piercing, and slashing damage

If you are able to cast spells, you can't cast them or concentrate on them while raging, unless they are spells granted by this paladin subclass.

Your rage lasts for 1 minute. It ends early if you are knocked Unconscious or if Your Turn ends and you haven't attacked a hostile creature since your last turn or taken damage since then. You can also end your rage on Your Turn as a Bonus Action.

Mark of Vicious Unforgiveness. As an action, you can mark a creature. The mark stays until you are incapacitated or you die. While it is within 5 feet of you, a creature marked by you has disadvantage on any attack roll that doesn't target you. n addition, if a creature marked by you were to provoke an attack of opportunity from you, you may use your reaction to do one of the following:

Make two attacks of opportunity at disadvantage.
Stop its movement by cutting the marked creature off by repositioning yourself 5ft in front of it.
Make one attack of opportunity at advantage.
Cast a spell granted by this paladin subclass.

Oath Spells

You gain oath spells at the paladin levels listed.

Oath of Devotion Spells

Rage Caster

Your anger casts your spells and smites your foes at the highest and most potent level possible. Use the warlock spell tables for the purposes of spell slots, and spells per day.

You may use your Channel Divinity: Somber Rage one additional time before needing a short or long rest.

Aura of Wrath

Starting at 7th level you, as well any friendly creature within 10 feet of you, gain a bonus to melee weapon damage rolls equal to your Charisma modifier (minimum of +1). A creature can benefit from this feature from only one paladin at a time.

At 18th level, the range of this aura increases to 30 feet.

Area of Absolutes

Beginning at 15th level, you are always under the effects of a Zone of Truth spell.

Any creature that fails saving throws against this is considered marked by your Mark of Vicious Unforgiveness.

Final Arbitration

At 20th level, you can use your divine prowess to sentence a for to a fate worse than death draining their ability to perform all but the most mundane tasks. When you successfully hit with an attack on a creature marked by your Mark of Vicious Unforgiveness after using Divine Smite, you may spend an extra spell slot. 

If you spend an extra spell slot this way, the creature must make a Wisdom saving throw against your spell save DC. For every 50 missing Hit Points, the creature has the DC of this is save is increased by 1. On a save, nothing happens. On a failure, permanently change all ability scores of the attacked creature to 8. That creature can not use any class abilities or features. 

Once you use this feature, you can't use it again until you finish a long rest.