Magic
Aspects
An "aspect" is defined as a specific type of light, manifesting as a single (magical) element. All sentient beings, including people, can conjure or manipulate an aspect. For example, someone with a water aspect is able to transmute pure light into water and control it at will. This person could also control water that is already present, such as from nearby rivers and oceans. Each person is born with the potential to manipulate a single aspect, and it cannot be changed.
There are nine aspects of light present in Luxos—earth, fire, water, wind, thunder, ice, bloom, radiance, and shadow. What aspect a person has can only be determined when it is casted, and generally cannot be "read" through other means.
Aspects are powerful and versatile, and society has explored many applications and techniques over time. However, despite its great potential, there is a limit to one's ability to use an aspect: as one uses it, a dangerous waste byproduct called "cael" is collected in the bloodstream where light once flowed. High cael buildup can lead to serious consequences (and ultimately death) if left untreated or unaccounted for.
Cael
Cael is a substance that manifests in the bloodstream in the place of light when magic is used. Like light, the composition of cael is not entirely underestood. Low cael buildup manifests as exhaustion, fatigue and muscle aches. Though cael within the body will dispel on its own eventually, rest and hydration will quicken the recovery process. Some people dispel cael more quickly than others due to a biological predisposition (such as a higher metabolism).
It's also been noted that spending time around other people, particularly loved ones, increases the rate at which someone recovers. Though concrete explanations are yet to be found, scholars speculate that this is due to a community survival instinct present in which people subconsciously "share" their light with each other.
In higher accumulations, cael may cause an individual suffer a condition known as caelism. Common tells for caelism include weakened or impaired bodily functions (such as difficulty breathing or slower injury recovery) and a telltale "bruising" or "blighting" across various parts of the body depending on the specific aspect. Caelism takes a significant amount of time to run its complete course before it is dispelled, and scarring from the blighting may remain even after a full recovery. Medicine exists to increase the rate at which cael is dispelled, but it's better to just never let things get to this point in the first place.
Though caelism is very dangerous, prognosis is rarely ever certain death. Caelism initially presents itself in a localized area - if aggravated, it will travel to the heart, where it will likely become fatal. Once symptoms are recognized, it is recommended that anyone with caelism find immediate medical care and rest accordingly. Of course, it's also considered common sense to avoid using more magic at all costs once caelism manifests.