Exchange of Healing

You touch an ally creature and channel your inner life force to cause a surge of natural healing. If the target creature has at least 1 hit point, it can spend one of the caster's Hit Die. They regain hit points equal to the total (minimum of 0).

A creature touched by this spell can spend one additional Hit Die when you reach 5th level (2), 11th level (3), and 17th level (4).