Biology
Despite being an alien species, the Aos Si have a very idealized human appearance, with males being considered very handsome and females very beautiful. Their body types range from lithe, to fit and well toned, with a lack of physical fitness or obesity being exceedingly rare. The heights of the Aos Si see a large variety of variation though, with individuals being as short as five feet, or as tall as seven and a half. Meanwhile, their skin color can vary from pale white, to fair, to dark browns, and even dusky charcoal in tone. The eyes of the Aos Si have even more variety, and can likely be found in almost any color. Despite this though, blue, brown, hazel, green, hazel, amber, grey, red and gold are the most common. Their pointed ears are perhaps their most defining feature though, and can range from large to small depending on their ethnicity. Interestingly enough, their own ethnicities are very similar to those of humanity, with those bearing Southeast Asian features consisting of a sizable proportion. In addition to this, the Elves have additional ethnicities that are fully unique to them, primarily with skin tones that are not found in the human population at all.
Anatomy and Physiology
Though the anatomy and physiology of the Aos Si is nearly identical to
humans save for a few small details, they are stronger, faster, and more precise. However, it is worth noting that they lack endurance on top of both reproducing and maturing much more slowly.
Muscles
Though the musculature of the Aos Si is nearly identical to human musculature, a few key differences set them apart. Human muscles are typically geared towards endurance, owing to the fact that they evolved as endurance hunters that ran down and exhausted their prey. The muscles of the Aos Si however, are very clearly configured for bursts of very precise speed and power, indicating that they were likely ambush predators in their far, distant past. The Aos Si are notably stronger in comparison to humans, but lack endurance in equal parts.
Eyes
While the average human is supposed to have a visual acuity of 20/20, the Aos Si poses superior eyesight measured at 20/15, meaning that while they may stand 20 feet away to see something properly, a human must come within 15 feet. Their peripheral vision also possesses superior clarity, and they are better able to see at night, but do not have true night vision. It is worth noting that the Wood variety have better visual acuity in low-light situations, but only the Dark variety have true night vision. Perhaps more importantly though, is their ability to just barely see magic, and its wind-like ebb and flow.
Aging, Lifespan and Reproduction
Throughout all literature, countless Aos Si have been documented as having lived for hundreds of years if not millennia. However, with more recent documentation, it is clear that this is far less common within the last few thousand years, with the average individual living for 300-400 years. Their longevity is directly tied to the presence of magic, as it sustains and rejuvenates them. Though they do age, they remain in their physical prime for the majority of their lives, and it is only towards the final decades that they show signs of aging. Even so, this is typically limited to whitening hair and the subtle changes in personality associated with such longevity.
Despite this great advantage over many other peoples, the periods in which the Aos Si are fertile is far significantly lower. However, being innately tied to magic, their ability to reproduce increases in the decades prior to major, threatening events. As a result, childbearing is bittersweet for the Aos Si. Though the coming of the child is joyous, it is a bad omen to them, as it likely means war or any other sort of strife is on the horizon. Or worse, right at their gates. Their offspring however, age relatively normally in comparison to humans, and following maturity, will eventually settle into a physical appearance that is both youthful yet indicative of their progress thorugh their lifespan, remaining fit throughout their lives.
Unlike many other species, the metabolism of the Aos Si is variable in accordance with the individual's needs. While others are more likely to starve to death or become obese from a lack or excess of caloric intake, they are less prone to such conditions. When deprived of sustenance, their metabolism carefully slows itself down to preserve the individual without excessively interfering with their individual performance. When pressed with a fight-or-flight response in this condition, their metabolism quickly goes back into a heightened state in order to allow them to act accordingly without hindrance. Meanwhile, should the Aos Si consume an excess of calories, their metabolism will accelerate in an attempt to use up the excess energy, increasing body heat in response. Due to cellular limitations however, this increase is only modest, and as a result, an individual can become obese with enough consumption.
This state will not last as they will revert to normal once their diet does as well however.