Necrotic energy is the merging of soul energy and unholy energy. It is used in life draining attacks like the aura of spirits surrounding death giants, a wizard's death spell, and other necromancy spells. Maen Grirngrim was the first to put this type of energy to use. He created the spells Consumptive Field from Healing Circle, Death Knell from Death Ward, and Slay Living from Raise Dead by changing some of the parameters of these spells and adding in necrotic energy.
Many schools of necromancy include both the study of necrotic and negative energy.