People
People in Luxos share the same biological foundations. They are humanoid and bipedal, and may have a pair of horns or a tail. While some may bear wings or gills, flight and underwater breathing is not possible without magic—though such appendages may decrease the amount of magic necessary.
Like all other things, people are composed of "light." It is entwined with their molecular structure, and commands life, growth and magic. As long as light is present, a great number of both physical and magical attacks can be endured before serious or lasting conditions occur. The recovery of injuries is carried out by the light within one's body drawing in untethered "pure" light that permeates the atmosphere.
Hearts
Every person in Luxos has a heart. This is what makes living beings (not just people) "alive"—as long as it is present and beating, light will remain affixed to the body and flow through it. It also keeps one's light from being used by others for casting, and what allows someone to cast magic themself. When someone dies, their heart ceases to function, and any light in their body will wash into the atmosphere, leaving behind an empty corpse. Should someone's memory and legacy be held onto by enough people, that person may become a Champion, and their intact light will persist onward.
Each heart is made up of two main components—the cor and the shield. A heart's cor, sometimes referred to as the "true heart," is the source and conduit of light within an individual. In people, its appearance is completely unique to each person. By contrast, monsters and animals all have a similarly-shaped cor with minor variations in hue or size.
The cor is encased in a crystalline structure known as the shield. In all living beings, the shield takes on the same form (a solid prism), though color may vary. A heart's shield protects its cor from impact and casting.
In general, if someone is injured, sick, or accumulating cael, they will eventually recover fully—even if some of the damage has reached the shield. Though the shield will also repair itself over time, repeated impact can breach it fully, leaving the cor vulnerable. Another individual with an aspect that matches the exposed cor would be able to manipulate the light within it, a technique that can quickly incapacitate or kill the other. Additionally, cael can leak into the heart and erode at the cor. Cor damage is permanent and extremely dangerous, so those who can help it will avoid it at all costs.
Revealing one's cor to another is considered an act of deep trust and admiration. Though it can also serve as an expression of intense love, the gesture has grown increasingly common—with that familiarity, some of its weight has faded.