Order of the Hemophage

Blood Hunters of the Order of the Hemophage believe in swift, ruthless revenge, using their enemies own vitality to replenish their own. Cursing themselves with a heavily altered strain of vampirism, they take a vow only to feed off the life force of those who wrong them first, in order to control their thirst. Most Hemophagic Blood Hunters find themselves driven into a frenzy during battle, satisfying their thirst for both vengeance and blood off of those who would wrong them.

Vampiric Blood

Starting at Level 3, your vampiric curse gives you the ability to use your enemies life force in place of your own... as long as it is done quickly.

Blood Pool

Your Blood Pool is a pool of hit points that fills as you take damage. Whenever you take damage from another creature, store 50% of the hit points you lost in your Blood Pool, rounded down. The creature that damaged you becomes Blood Marked until the next time you end your turn. At the end of your turn, the Blood Pool empties, reducing itself down to zero. 

The amount of health you store increases as you gain levels in the Blood Hunter Class, becoming 66% at Level 8, 75% at level 11, and 100% at level 18.

Vampiric Strike

When you hit a creature that is Blood Marked with a weapon attack, you may spend points from your Blood Pool up to the damage you dealt to that creature to heal an equal amount of hit points. You can only use Vampiric Strike once per target per turn. 

Crimson Martyr

Whenever another creature within 30 ft. of you gets hit with an attack, you can use your reaction to manifest a shield of your own life essence to halve the damage done by that attack. You take necrotic damage equal to the amount of damage reduced. This damage cannot be reduced or avoided in any way. The creature that made the triggering attack is considered the source of this damage. You can use this feature a number of times equal to your proficiency bonus, gaining back all uses on a short or long rest.

Optional Rule - Multiclassing: While benefiting from any effect from another one of your classes that grants you resistance to any type of damage, your Blood Pool cannot fill from damage taken from that resisted damage. Vampiric Strikes do not account for the damage added by other classes features, such as Divine Smite or Sneak Attack, meaning you cannot heal from damage dealt by those features.

Bloodied Vengeance

Starting at level 7, your weapon attacks against Blood Marked creatures gain a damage bonus equal to your Hemocraft Modifier (minimum of 1). Additionally, your Crimson Rites deal an additional Hemocraft die worth of damage to Blood Marked creatures.

Exaltation

Starting at level 11, if your Blood Pool reaches zero due to you healing from Vampiric Strikes, you become Exalted.

Exalted: Until the end of your next turn, you have advantage on attack rolls against any Blood Marked creature, and your attacks on such creatures score a critical hit if you roll a 19 or a 20.

Bloodless Exaltation: The loss of your own blood can drive you into a delirious, blood-frenzied state. When your Hit Points drop below 33% of your maximum hit points (rounded down), you become Exalted until the end of your next turn. You can only become Exalted this way once per Short Rest.

Blood Curse of Vengeful Malice

Starting at level 15, as a bonus action, you can expend a use of your blood maledict to curse Blood Marked creature you can see within 60 ft. of you.

For the next minute after being cursed, the target is always considered Blood Marked. As an action, the creature may make a Charisma Saving Throw against your Hemocraft Save DC to remove the effects of this curse.

Amplified: You can use Vampiric Strikes on this creature multiple times per turn while they are cursed.

Blood Rush

Starting at level 18, constantly losing and regaining the blood in your veins has sped up your attacks and speed. Whenever you score a critical hit on a Blood Marked target, or kill a Blood Marked target, you gain the effects of the Haste spell until the end of your next turn, not requiring concentration. You do not suffer the effect of lethargy as a result of the Haste effect ending if it was gained in this way.