In Patch 2.3.0 for Path of Exile, Spirit Offering is going to be a new skill that completes the necromancer offering skill trilogy.
Spirit Offering consumes corpses to grant a portion of physical damage added as chaos damage and a portion of life added as energy shield to your minions when it is used. The more corpses consumed, the greater the energy shield granted. It also instantly recovers the same amount of energy shield, so can be used to save your minions that are close to death. Like the other Offering skills, Spirit Offering’s buff effects lasts longer for each corpse consumed.