I wrote this in an other thread, developing from my thoights here.
Re the concept of "vampiric healing". It is undeath. It should never be actual healing. It is a pale imitation of life. Its mechanics should differ from healing. Vampiric healing is undead and nonliving. It is about animating a dead body, not restoring a living body.
The positive energy is a mystic source of conciousness, life, and success.
The (Deep) Shadowfell is low energy ether. Ghosts rest. A ghost would need to gain energy to enter the neutral (Shallow) ether to manifest lifelike in the material plane.
The (Deep) Feywild is also ether, but high energy, more than the material plane can normally contain.
Undead exist naturally, as aspects of a person resting in the Shadowfell. A restless undead is rare but famous. Often it is said, there is unfinshed business in the Material. Somehow this connection to the Material is literally energizing the ghost, that would normally be resting. In other words, they are utilizing positive energy, without processing it normally the way material living creatures do. Typically, the restless undead are minds, manifesting a virtual body ethereally as a ghost. A powerful mind can "haunt" the material persons or places that remain unfinished, influencing mentally or poltergeisting physically. The restless mind maintains a link to the corpse. Sometimes an exceptionally powerful can even animate ones dead body, whence the concept of a sentient undead. A vampire is such an example of a sapient corpse.
When a vampire sucks life energy from a living creature, there is no healing. The body is dead. There is nothing to heal, or that could heal. There is no cellular metabolism. But like a golem, the corpse moves around anyway.
Instead of the body gaining the positive energy to become whole, the vampire is energizing ethereally. Higher frequency ethereal energy means the vampire can avoid resting. The undead mind stays alert and manifest.
Thus vampiric energy gain is an addiction. The vampire depends on it to maintain material existence. Without it, the undead mind would rest, and the corpse collapse - as corpses normally do.
Vampiric "healing" is no healing. It is a pale imitation of life. It is a mental manifestation of a faint memory of what life was once like. Vampiric energizing is more like a quasi-real illusion of life.
Actually, the body of a vampire has zero hit points, being quite dead already. This material avatar of a vampiric ghost is made out of temporary hit points. To maintain these temporary hit points, the vampire must continually feed on the living, or else suffer one level of exhaustion each night if without feeding. When the temporary body dies of exhaustion or the temporary hit points run out, the body collapses. Then the vampire reverts to a ghost and loses the exceptional influence over the material plane. Nevertheless this ghost might still have unfinished business to attend to, is a powerful mind, and might reanimate ones corpse at some future time to manifest as a vampire once again.
While restless undead are freak occurances, they are natural in the sense that the multiverse functions this way. A necromancer is someone who researches and manipulates the magical processes that are in play during a restless undead manifestation event.
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