Close Wound

You touch an ally creature and channel their 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 its Hit Dice as a reaction.  Special: This spell can be cast as a Action or as a Bonus action but only 1 time per round.  

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).