Magical Race or Species?: Yes
Some Aelfyn can be corrupted by the Goddess of Blood and Shadows. However, this usually drives them completely insane.
Sedayin magic is innate but needs to be unlocked at the Golden Well of the Sunfolk or with the Song of the Storm (Sheantyar only). This is usually done for children, or young adults of their race, if it is so wished. As the use of the arcane puts a severe strain on the Fea, only about 20% of their populace will unlock their arcane powers. All others exist with their innate locked powers, which mainly manifest as a strong affinity to their inborn element/environs, be it the sense for the Woods, the Ice, or the Sea.
Unlocked arcane abilities range from fostering life (tree-singing, healing) over element singing (weather manipulation, calling for rains/storms), to active skills against the shadow. There are numerous blends of those skills, and about each society among the Sedayin has their own preferred talents they seek in their members.
To Sedayin, their arcane use manifests in songs and patterns, strands of the power (or the elements) interwoven to achieve a specific effect. Most peaceful skills have songs, most combative ones have patterns.
Sedayin will say that Healing is a song or pattern made of pure arcane power, soul-energy, and water and wind. Those patterns (their books recorded about 800 different patterns and songs for healing) are directly immersed into the injured/sick body and push the physical material into a healthy form. Depending on what song is used, this can mean, an injured person who should die, does not, wounds suddenly heal, or heal to a point like they had weeks of healing already, bones set, and the flesh is purged of disease and infection. Healing is extremely straining for the healer performing it, and healers are the prime candidates for drawing on more power than they can safely handle, damaging themselves in the process. They also have to handle the pain of the wounds, as they share the suffering of the patient. Battlefield healers often are limited in their healing skills but developed the skill to transfer their own life essence to a wounded patient, a dangerous technique that has killed many of them.
Battle skills are a varied bunch, from hiding, moving unseen to shielding against the arcane to directly attacking the mind and body of the enemy. Sedayin do not have skills of a scale that can level cities, or destroy entire groups of enemies at once, but they do use what they have rather effectively.
The main limitation of Sedayin magic is the balance of Fea and Ari. Using too much of one’s power results in strain to the Fea, a weakened Fea loses its link with the body, and thus the fading can set in. A Sedayin drawing on more power than is safe will suffer physical damage, from loss of body mass to open injuries along his body, and even if he survives the experience, he may never recover.
Many Sedayin can only use their arcane powers, or their full powers, when close their natural element, meaning the Sea for the Sheantyar, the Ice for the Frostfolk, the Woods for the Elcarin. Separated from those, the powers will weaken or fail completely.
Sedayin do not regard the arcane as unnatural; on the contrary, they see the arcane as supremely natural and part of the natural laws and mechanics of the world. Their careful approach to those powers comes not from the experiences in Uthuria, but from knowing how easily they can damage themselves with those powers. Once a child has its powers unlocked, it will be taught all it can learn. Usually, the parents or the young Sedayin already know what way they want to go, and what society they intend to join, and that’s where their training happens. Mindful of their limitations, Sedayin, excepting healers, do not easily tend to overstrain their powers or experiment wildly. Sedayin do not care about “becoming powerful,” they often prefer to specialize in a few skills and use them extremely well.
The Sheantyar and the Arcane:
The Sheantyar do not practice the same arcane ways as their Sedayin brethren. They habitually unlock the powers of many of their children and practice a wilder, much less-finely trained way in their powers, which are deeply linked to the Ocean. Sheantyar are skilled in manipulating their surrounding seas, guiding waves, calling mists, even calling storms, they do have healing skills and other typical Sedayin talents, but their entire practice is not as carefully forged as the other Sedayin’s. Sheantyar are known to take great risks with their Fea, burning themselves out early, wielding more power than they can safely handle when necessary. A healer may bring himself to the brink of destruction, healing others, only to let his exhausted body slide into the waves and dissolve into green sea-foam again. This is regarded as the natural way for them, the Fea rules, the body lasts as long as it can, and when it fails, the fea returns to the Sea.
When the islands of the Sun, before the coast of Xia, sent an armada north to punish the Vanir, they also came after the Sheantyar, whom they considered allies of the Vanir. In the joint battle against the Xian ships, about 120 Sheantyar deliberately sacrificed themselves, sending their fully healthy fea into the waters, drawing the sea to them, wielding the waters themselves against the Xian fleet, while more sea-callers wielded lightning and wind in concert with them. 120 Sheantyar dead… and an entire armada crushed in a storm like none other. The stories of the raging souls at the heart of the tempest have become staple among the scary stories along the coasts.
Generally, Sheantyar have a keen eye for when it makes sense to use their powers, but when they do, then they do it full force and with utterly no regard for their own survival. Because for them, there is no death, only the return to the Sea. Sheantyar arcane skills are so strongly linked to the sea that even healers practice their art, preferably close to the waters if they are not on ships already.