Hit points (and magical healing) are often cited as an element of D&D that doesn't make sense--if they represent physical health and damage, then why doesn't your performance decrease as you take damage? If they represent reserves, resilience, and luck, how does healing work? Why can a high-level character shrug off blows that would logically obliterate a lesser character and survive a slit throat while sleeping? Why do characters (including monsters) regain all their health overnight?
This post discusses answers to these concerns in the context of Quartus, the world in which Dawn of Hope takes place.
What a brave new world, that hath such people in it!
The first important realization is that Quartus is not Earth, nor are the peoples of Quartus identical to those of Earth. For convenience we call the dominant intelligent life "humans," but the physical and biological principles that describe how they function differ completely. Unlike Earth, the irreducible particle of matter is a form of energy called anima. Anima is produced by intelligences as they learn and grow. Those intelligences (called Sparks) gather and organize this anima into body and nimbus, the physical and the spiritual. These bodies are composed of concentrated anima, just like every other entity and object. Organs pump various anima-enriched fluids around the body, extract processed anima from food, and support and move the body at the command of the Spark. Unlike earthly bodies, there are no cells that reproduce by fission--if viewed under a microscope, a Quartan organ would appear to be composed of inert matter. Only under the influence of a nimbus does this inert matter take on the semblance of life. Once the body dies (either violently or otherwise), the inert matter slowly dissolves with no nimbus to hold it together.
This has several consequences. First, the healing rate of a Quartan is dependent on the connection between the Spark and the body, mediated by the nimbus. Effectively, the bottleneck is the speed at which the Spark can concentrate ambient anima and funnel it through the nimbus to the injured part of the body. This takes time--urgent needs are met by drawing from a reserve of concentrated anima stored in the nimbus. Second, wounds are rarely fatal unless the anima required outstrips these reserves of concentrated anima. Smaller wounds are effectively "patched up" by infusions of reserve anima, allowing combat to continue. Once the reserve is fully depleted, any further significant wounds will sever the Spark from the body, resulting in death. Third, as a Spark gains in power (experience), it becomes more adept at concentrating and storing anima. This allows an experienced Spark to sustain much more damage to its body before it ceases to function.
As a side effect of all of this, diseases and toxins tend to act to disrupt the connection between nimbus and body, slowing or stopping this repair process. Diseases and curses that affect the mind (the nimbus and Spark) are the most feared; bad moods and destructive thoughts/habits can be contagious.
What does this mean for Hit Points?
Hit points are a quantification of the amount of reserve anima a particular Spark has available. As a Quartan takes damage, its reserves are depleted repairing that damage. When those reserves are depleted, death results. Until the reserves are gone, functionality is unimpaired. Creatures of higher power (higher level/hit dice) have larger reserves, as do those whose focus is on training the body such as fighters, paladins, and barbarians. Those who focus on training the nimbus to resonate with the ambient anima to cast spells naturally sacrifice some of their reserve to this purpose, resulting in lower maximum hit points.
Yes, that means that a high level fighter can take the breath of an adult dragon and not be impaired. It does significantly deplete his reserves of anima. A barbarian learns to suffuse his skin with reinforced anima in a state of primal rage and thus reduces the damage taken by physical assaults. Nimble characters like monks and rogues gain an instinctive ability to project their nimbus slightly outward to deflect the fire of a breath weapon or an area spell, protecting them from its damage.
Temporary hit points usually represent an additional layer of anima coating the nimbus. Like ablative armor, it is sacrificed to prevent (or repair) damage without tapping the Spark's reserves directly.
Natural Healing and Hit Dice
Given breathing room and an hour's rest, Sparks can pull from deeper, less easily mobilized reserves to refill their ready reserve. This is represented by spending hit dice on a short rest. These reserves are slower to refill--it takes several nights rest to do the job, whereas the ready reserve refills overnight given good sleep. While the body is offline in sleep, the Spark can devote its full attention to concentrating ambient anima. This does raise the question--what happens if you rest in an area of minimal ambient anima (such as an area heavily polluted by undead)? That's a question for another day.
Magical Healing and Healing Potions
Spells such as cure wounds and healing potions operate by providing a ready supply of "pre-digested," pre-concentrated anima in a way that is easy to incorporate. This quickly fills the ready reserve and restores function to an unconscious Quartan.