Blackened Knight

By choosing the Blackened Knight subclass, you choose to be an Unfettered Blood Knight who lives purely for battle and has near zero limits in their pursuit of it. This is someone who not only wants to fight constantly but will burn down anything and everything just to keep their war going. They might instigate violence for fun, seek out gods or monsters just to see if they can kill them, or because they are curious how their skills compare, and abandon or endanger alliances or friendships that get in the way of the next challenge. They're like a self destructive perpetual motion machine of hurt, driven by an unquenchable thirst for violence and entirely unhindered by cowardice, conscience, or consequence. Doomed from the very start, and chances are, they don't regret a second of it.

Bolstered Training

You gain proficiency in shields, martial weapons that don't have the Two-handed or Reach properties, and hide, chain shirt, scale mail, and breastplate armor.

Relentless Opportunistic Fury

When you make a critical hit, you can use your reaction to make an opportunity attack as well. If the opportunity attack hits, you add your Constitution modifier to your AC until the end of your next turn.

Perfect Technique

Starting at 9th level, you can use your cunning action to begin concentrating at the end of your turn. as long as you are concentrating on your Perfect Technique, you gain two extra attacks on each of your turns.

Violent Excitement

At 13th level, whenever a combat starts, from the beginning of your first turn to the beginning of your next turn enemies will have disadvantage to hit you and anything of your choice within 5ft. of you. if you do end up being hit by an enemy before the effect ends, it can extend until the end of the next turn from when it should have ended, this can continue a number of times equal to half your level rounded down or the end of combat, after which you need to take a short or long rest before you can extend it beyond the initial runtime again.

Untethered Strike

When you reach 17th level, you can, for 5 time per short or long rest, enhance any melee attack. An attack improved in this way has advantage to hit and does an extra 6d6 damage. This cannot be used with a sneak attack unless its during a surprise round.