Balance of Life

You choose 2 creatures within range:  One to give, and one to receive.  A ghostly green beam of light connects the 3 of you.  The giver feels the chill of the grave as their life essence is drained from them; a portent of death to come as they recieve 1d6 of Necrotic damage.  The receiver feels a rush of heat and comfort as they recieve 2d6 of healing.  You, as the conduit between the two lose 1 hit die slot  until your next long rest.  This brings the transaction balance to zero as there is no such thing as free.

*Casting at a higher spell level increases the damage by 1d6, the healing by 2d6, and loss of one extra hit die slot per level above 2.