Lunechondria

The Secret to an Ageless Seven Centuries

Lunechondria are a special type of microorganism that thrive only in the bodies of Elves. It is said that part of why Elves age so slowly is because of the Lunechondria in their blood feeding off of mitochondrial decay and preventing their bodies from recognizing they are growing older.

Microorganisms from the Moon

Lunechondria are too small to be perceived with anything other than enchanted sight, as they are only a fraction of the size of a cell, the same size as the mitochondria they feed off of.

Selene by Jarhed

Their origins have been traced back to the moon, likely as creations of the Goddess Selene herself, Goddess of the moon and creator of Elves.
It is said that, under close scrutiny, the organisms almost resemble the moon itself. A slice of heaven manifest in the mortal body, which is what gives some Elves the idea that they are superior to other mortals, as their bodies sustain these beings.
Some Elves even believe these are not independent beings, but are instead extensions of their own lifeforce, however all scholarly efforts into this theory have proven it to be false. Lunechondria are more like symbiotic creatures, benevolent parasites that latch onto Elven organisms and live off of their decay.

Biology and Benefits

Lunechondrian biology is still largely unknown. How or why they evolved to sustain themselves off of mitochondrial decay is still not known. Perhaps it was a blessing for Elfkind by their Goddess. Perhaps Lunechondria needed a way to survive inside of a body without eating away at it entirely. There is no certainty in these hypotheses.
Whatever the reason, their diet consists entirely of mitochondrial decay. As the body grows older, the organelles begin to to decay and impair the body in many ways, most notably by physically aging the body and manifesting those years as new changes.
Elves, however, live to be upwards of 750 years old, and the average Elf will not show many effects of aging until they reach 700. This is due to the fact that mitochondrial decay cannot last in the body of an Elf. The instant decay begins to envelop a mitochondria, its root is eaten by the Lunechondria and it stops effecting the body as it would otherwise. Only at 700 do Lunechondria flee the body, growing either too tired with the host or sensing it is nearing an end that they do not wish to be around for. This is when decay takes hold and an Elf begins to age.

Licvan by Jarhed

Drawbacks

The greatest problem with Lunechondria is that not every Elf can have it, or if they do, not all Elven bodies can keep it. If an Elf gets particularly sick, it may spread to the Lunechondria and kill it. If an Elven body begins to age without Lunechondria, it will feel the effects far more. Another great killer for Lunechondria is stress, which is why many rulers from the Nerifir family have experienced rapid aging on the throne. The stress of being monarch is killing their Lunechondria and aging them far faster than their bodies can handle.
Lunechondria may leave an Elven host body if they are not getting the sufficient nutrients. For instance, Elves that undergo processes to become a Lich, like the famed Licvan, poison their Lunechondria by becoming a Lich. Any other form of stopping aging may also drive away the Lunechondria, except for Druidry, which only creates more nutrients for the creatures.
Lunechondria can also get too frenzied in eating the mitochondrial decay, occasionally eating the mitochondria itself. When this is done, not only does aging begin to take effect more rapidly than usual, but cells begin to die and the body loses energy.