This subclass allows fighters to sacrifice their own life in order to improve their own strength. By trading hit points fighters of this subclass can power up their attacks or natural attributes. They can also absorb the maximum hit points of other players into their blade. 

Shukketsu no meiyo (Bleeding Honor)

At the 3rd level you forge a bond of blood with your blade. Through this bond you may infuse your sword with your own blood. By sacrificing either 1d6, 1d8, or 1d10 life points you may additional damage equal to how much life you sacrificed. You also may reduce the damage you deal by 1d6, 1d8, or 1d10 to heal damage equal to your roll as you attack. 

Nagori yuki no omoide (Memory of the Fallen Snow)

At 7th level you have become one with your blade's thirst for blood, and have learned how to enhance your abilities further.

Bloodsucking Universe. When you deal damage to an enemy you may reduce their maximum hit points equal to the amount of damage you deal. This ability can be activated once per short rest. This ability gains an extra use for each martial archetype level gained by the player. 

Shizuriyuki. When you deal damage to an enemy you may mark them. The target is marked for 5 minutes. When you strike the marked target you may absorb health equal to the damage you have dealt to them. You may use this ability once per long rest. This ability gains an extra use for each martial archetype level gained by the player. 

 

Buraddoreiji (Blood Rage)

Starting at 10th level you may enter the blood rage state. While in blood rage state you gain a bonus to all stats equal to your constitution bonus, and you may add damage to your abilities equal to your constitution modifier. As a drawback for each second you remain in blood rage you take 1d4 of damage and you cannot be healed until you have existed the blood rage state. At 1 hit point you will forcibly exit blood rage state and be stunned for one round. 

Zansetsu (Lingering Snow)

At 15th level you may sacrifice your life to engulf your blade in blood, dealing a massive, ranged strike with your sword. You may sacrifice up to 10d10 hit points to deal 10d10 damage. This slash can hit up to two targets within a 10 ft. radius of each other. The targets must make a constitution save, and if they fail you absorb health equal to half the damage dealt by this blow. The range of the attack is 60ft. This ability may be used 3 times per long rest. In blood rage mode this attack deals an extra 5d10 damage. 

Chimamire no Yukibana (Bloody Snow Blossom)

At 18th level your mind and your connection with your blade have evolved so much that you are able to fade into the universe itself. When this ability is activated the user instantly enters stealth as a cloud of blood red snow descends on the battlefield. While they are in this state they can not be detected by any means except true sight. They may exit on command, or by launching an attack. Should they choose to attack from this state their attack is made with advantage, a +5 chance to hit, and +20 to damage. This ability may only be used once per long rest unless the user is willing to sacrifice 99% of their remaining hit points in order to use it a second time.