Shed Blood, Give Blood

Pure intent and the will to protect has given you the ability to heal, at the cost of your own health.

When taking slashing, bludgeoning, piercing, or acid damage, as an action (or reaction if it isn’t your turn), once per turn you can choose to heal an ally by the damage you take plus your Blood Hunter level and proficiency modifier. 

If you use this ability on an attack that renders you unconscious, roll a d20.

On a 20 the target heals 1d8 x your Blood Hunter level and gains temporary hit points equal to your Blood Hunter level plus your proficiency modifier. On a 5-19 the target heals as normal. On a 4 or less the target heals as normal, but also takes 1d4 psychic damage.