Transfusion of Blood

As part of casting this spell, you must expend four Hit Point Die or the spell automatically fails as you expend blood from your body taking necrotic damage up to half the roll of the hit point die that can't be reduced or negated in anyway, but gaining temporary HP equal to the roll. When you target a creature with a spell or feature that heals, you can increase the healing by your constitution mod and heal yourself the same amount of your constitution mod as well, you can also as part of the same action, transfer any remaining temporary HP to the target you have left on you. 

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, you can roll an additional hit point die for each slot above 4th.