Martial Archetype - Blood Knight
The archetypal Blood Knight employs their own flesh and blood in the slaughter of their enemies. To a Blood Knight, battle is everything. It isn’t winning or losing that drives them so much as it is the opportunity for a good fight. And when they find that fight, they use everything they have to contest their opponent. They utilize blood sacrifices to grant themselves additional offensive and defensive capabilities, though at a steep
Beginning when you choose this archetype at 3rd level, you gain the ability to utilize your health to enhance your attacks and defenses. You gain the following features:
Sanguine Slice. Whenever you hit with an attack, you may sacrifice a number of hit points and add the amount sacrificed to the attack’s damage roll. The number of hit points sacrificed cannot exceed triple your proficiency modifier.
Sanguine Block. When another creature hits you with an attack, you may use your reaction and sacrifice a number of hit points, gaining +1 AC against that attack for every 3 hit points sacrificed, potentially causing that attack to miss you. The number of hit points sacrificed cannot exceed triple your proficiency modifier.
You may only use Sanguine Block or Sanguine Slice once per round, and may not use both in a single round.
Scent of Blood
Starting at 7th level, you gain advantage on any Wisdom (Perception) or Wisdom (Survival) check used to find a wounded creature.
Additionally, as a bonus action you can sacrifice 1 hit point to learn the general direction of every creature within 100 feet of you that has blood.
At 10th level, you can use your bonus action to sacrifice a portion of your health and enter a Blood Rush. For every 3 hit points sacrificed, you gain the effects of a haste spell on yourself for 1 round. This haste effect cannot last longer than 1 minute. When the effect ends, you suffer one level of exhaustion.
Strength of the Wounded
Starting at 15th level, you gain increased power when below half of your maximum health. Whenever you use your Sanguine Slice or Sanguine Block features while below this threshold, you gain double the effect for each hit point sacrificed.
At 18th level, your sacrifices only take away a portion of your power. Whenever you sacrifice a number of hit points, you gain an amount of temporary hit points equal to the hit points sacrificed. These temporary hit points last for 1 minute.