undying taste

you heal 1d6+spell casting modifier necrotic healing and for the next minute, the creature makes a saving throw when dropped to zero hit points.  a DC 13 CON save on a success the creature drops to 1 hit point    

casting it at 2nd level adds 1d6 and drops the creature to 5 hit points for every level above 2nd adds 1d6 and raises hit points by 5