Coagulation

This is Haematomantic Magic. You touch a living creature, granting it a measure of magical enhancement to their natural vitality. If the target drops to 0 hit points during the spell, any death saves made by the creature are made with advantage, and on three successful saves, instead of stabilizing, the creature is brought back to 1 hit point.

A creature with three failed death saving throws still dies as normally, and this spell has no effect on undead or constructs.