#healing factor

Unlike humans, a dragon's stem cells never fully turn off, allowing their body to fully regenerate any damage given enough time provided nothing fatal has occurred. If enough of their heart remains that it still beats, then any damage that has been done to it can regenerate and fade and leave them with a heart that is quite literally as good as new.

In some ways it is as if dragons never really leave the egg, and are constantly in a state of explosive growth which is kept in check by specific genes whose sole purpose is to monitor a dragon's body plan and determine when something has been lost or is out of order. These genes are exceptionally robust and resistant to mutation or damage, and on top of a dragon's naturally high resistance to radiation, means that even things such as cancer are exceptionally rare to find in a dragon body.

Like many things with regard to dragon physiology, it is unclear how much of this stems from natural evolution and how much came from the dragons' meddling with their own genomes in past attempts at guided evolution, as theirs is a species just as advanced and multiple times older than our own, but what is clear is that part of what makes their regenerative power so robust is the way that their bodies are structurally designed.

The size and mass of some dragons can on occasion far exceed what would ordinarily be allowed by physics. Similarly, the sheer amount of power a single dragon can seemingly store and generate through spellcasting also appears as though it is bending some sort of rule. But reccent study of dragon physiology has revealed the trick that makes such feats possible, which may also go some way to explaining the potency of their regenerative prowess.

Throughout every cell of every bone, muscle, cartilage, scale, or fleshy tissue on a dragon's body, tiny, microscopic pathways similar in appearance to arteries or veins can be found. Thicker and more robust in some areas or microscopic and innumerable in others, these veins are not made to carry blood or nutrients throughout a dragon's body, but rather ruach, the word dragons use for the energy from which they mold and cast magic.

Having origins in ancient Hebrew, ruach could be translated as something akin to 'breath', particularly in the sense of something more metaphorical or divine, like a spark or 'breath of life'. It is the philosophical belief of most dragons that ruach is something which exists in all living things, but which they themselves have an overabundance of and the capacity to tap into and transform to achieve various effects. It is through the use of ruach that a dragon can breathe fire or summon storms, and while modern dragons are at best largely agnostic, there remains a sense of mysticism or undiscoverability amongst their kind as to the true natures and origins of this energy.

These crisscrossing networks of magical energy flow are the means by which magic is utilized and applied to every part of a dragon's body, and their overall number and density determines the "pool of magic" a dragon has at their disposal to draw from and bounds the upper and lower limits of their energy. The shape, orientation, and patterns created by these pathways of energy also go some way in determining the "element" a dragon is bound to, such as Ice or Fire, as they give any magic generated from the flow of their ruach a specific shape or nature intrinsic to that dragon. This is also why every dragon's manifestation of their element is unique, and how one dragon's flames can heal and another's can melt stone.

But these veins of ruach are for more than just magic. They are what reinforce a dragon's body against physical forces and allow them to achieve shapes and sizes that would otherwise not be possible for man or machine. Their bodies are made up of energy as much as they are matter, in some sense, which is how they are such sturdy, strong, long-lived creatures. It's how the scales of a sea dragon can be so dense as to repel any modern human weapon short of a ballistic missile, including any manner of armor piercing round, yet also remain lightweight and flexible enough to form the outer skin of a living creature.

And it is also these veins of ruach that help a dragon regenerate so efficiently. Indeed, their healing factor could be considered a sort of natural magic all its own, something the dragons never need to learn how to use, as much as it could a biological process of their organic bodies. It is the fact that it is these two things in concert, and the later understanding and manipulation of both via genetic engineering and magical study and application, that has made them so successful as a species.

So then, does this mean dragons are immortal?

No.

As one example, a dragon can still be killed through harm if the level of damage done exceeds that which can be regenerated before they bleed out. Without the active application of a proper spell by another dragon, regeneration takes time - days of it - before the dragon can return to normal function. You may think then that one need only apply a constant healing spell upon themselves to become invulnerable, but this misunderstands regeneration as some sort of spontaneous creation from nothing.

Rather, a dragon's regeneration rebuilds from what is still there, with every distinct part or system of a dragon's body having its own "map" which its genes can read and build off of to restore what's been lost or damaged. But, each map is distinct to that part or system, meaning if say the entirety of a dragon's liver is destroyed or removed, and there is no longer any "liver map" to build from, the dragon cannot just spontaneously create a new one, nor could they take cells from nearby tissues and create a replacement.

At least, not on the fly - while possible, this is a sort of invasive magical surgery and a procedure only the most skilled healers are capable of performing, and is not without its complications and limitations to the healed dragon. The process in which these cells are removed and reshaped constitutes a sort of damage the dragon cannot heal from, leading to one of the only ways a dragon can receive permanent physical harm or scars, and will leave whatever part of the body the donor material came from damaged for life.

Different body parts require donor material from different areas, with some being more impactful for others, and then the "programming" of those cells with a "map" for whatever organ or part is being replaced is another feat entirely which requires yet more time and expertise to perform. As such, the total loss of an organ is potentially deadly to even a dragon, and if too much harm is done to their body too quickly, even regeneration will not restore them before they expire.

Even still, this leaves dragons as remarkably sturdy creatures indeed. They show no wear or visible signs of age after reaching maturity until well over a dozen centuries have passed, and the rate of growth for a dragon is quite explosive and brief as compared to other life on Earth, particularly in comparison to their lifespan. A dragon will grow more in the first 12 years than it will for the next 1200, and by the age of around 30, a dragon is fully matured and functionally the same for the remainder of its lifespan, which for some races can extend up to 2000 years.

The lifespan of a dragon is also determined by the number and density of their ruach veins, as well as how they use their magic and their overall health and diet. It is not unlimited, but it far exceeds that of any ordinary human, with only select neo humans having abilities which allow them to approach such epochs of time. Dragons also do not scar naturally, and all their regenerative physiology extends even to halflings who are as much human as they are dragon, meaning no matter the harm, if they can survive, most will never look any worse for wear after the fact.

But... there is an exception.

In ages past, when dragons still fought wars amongst themselves, it became necessary that real, lasting harm against one another be a possibility. In the magical arms races which occurred in these times of inter-clan conflict before the Empire Era, a particular brand of magic was developed, known today colloquially as Dirty Magic, which not only bypasses but permanently shuts down a dragon's regenerative healing factor by not just damaging their ruach networks, but decaying them entirely.

In some sense, it could be seen as a sort of senescence magic, where the harm done by the spell not only damages the dragon's body, but attacks their magical energy pathways and physically ages them to where they would only naturally be at the end of their lifespans. This prevents energy from flowing quite as freely, and entirely shuts down the regenerative properties of a dragon's cellular biology by preventing ruach from assisting the dragon in their regeneration.

This leaves visible scars not unlike those humans would acquire anywhere that this "Dirty Magic" has struck and done visible harm, and today can mostly be found among some of the oldest or most combat-oriented of dragons. Li'alie Ninoke, former captain of the Royal Guard, for example, as the utmost enforcer of the empire's laws and values and defender to the King, entered into many skirmishes with other dragons in her lifetime, some of whom hoped to use Dirty Magic as a means of felling her, leaving her with two prominent scars on her face. Or Master Elheim, Aldaron's chief elder and part of the King's Council, who has been completely blinded in one eye with a prominent scar down the right side of his face from a war injury sustained in his youth.

Dragons then are incredible creatures with which even some of the most remarkable neo humans would struggle to compare, but they are not perfect, and they are far from immortal. But it is a testament to their resilience and their ingenuity that they have persisted for as long and successfully as they have, with dragon society as a whole extending back close to two million years. And while there has certainly been much turbulence and multiple total collapses and reinventions of civilization as a whole in such exceptionally long periods of time, dragons have stood tall all the while.