Mordenkainen's Lost Notebook
3-level Necromancy
You choose one creature you can see within range to benefit from this spell. If the affected creature’s hit points are reduced to 0, it remains conscious and can act normally on its turns. However, if the recipient takes damage from a single blow that would reduce its hit points to a negative amount equal to its normal hit point maximum, then it immediately dies. Likewise, if the spell ends while the recipient’s current hit points are 0, then it falls unconscious and misses its first death saving throw. If the creature dies while under the effects of this spell, it can be raised from the dead by normal means.