The Fundamentals
What Is Magic
Magic is thought to be a force that is tied to all things of existence, which can be used to manipulate the energies of the world (including but not limited to reality, time, and the very souls of creatures). Magic can appear in many forms, and is often the term given to a power or object that defies the studiable laws of sense. Magic is a source of energy for enchanted items and spellcasters, and it is what binds all planes and things together.
The Four Types of Magic
Arcane
Magic associated with the Leylines (and the study thereof).
Divine
Magic associated with Divinity.
Primal
Magic associated with Nature and the Elements themselves.
Supernatural / Occult
This type of magic does not fit into the other three categories; it is the least comprehensible and most varied. This magic is associated with all Regalias, Warlocks, and Blood Hunters.
Mana
Magic can be tapped into through the use of Mana, which is an invisible resource that all living creatures and entities possess. To some, their Mana is insignificantly small and thus near non-existent, but to others who are able to nurture and harness their Mana, they can access the Weave and use Magic. Hence, spellcasters exist.
That said, Mana has been known to be used for things outside strictly casting spells/using Magic. The most common example of this is using magical objects. Nearly every creature can use such things, but those that lack a true body cannot (like most undead, familiars or other conjured creatures). A less common example of using Mana are Monks, who are able to use their Mana to greatly strengthen their minds and bodies—a process they refer to as using, "Ki".
Spellcasters & The Manamyxx
Some believe Mana is stored in the mind, and others believe it is stored in the soul. Neither has been proven true, but the utilization of Mana and Magic definitely shows signs in the physical body. Known as the, "Manamyxx", a small spherical organ can often be found near one's center of gravity (usually their navel or "belly button"). All people possess a Manamyxx, with the size of it reflective of one's capability with magic; as one's capability grows, so does their Manamyxx. Outside of people, though rare, it is not unheard of for an animal, monster, or even a plant to possess a Manamyxx.
As such, most people in Agathok believe that Mana is stored within the Manamyxx, and yet even when it is torn out, nothing suggests so. Not only that, but even when it's torn out, a new one quickly grows elsewhere on the body, moving ever so slowly back to its original spot. Even with it torn out, a creature is still capable of casting spells. Perhaps even stranger than these facts, are that the more a spellcaster pushes their use of magic, the more inflamed their Manamyxx and the tissue around it becomes. Sometimes this inflamation can burst resulting in what is called, "Mana Burn": permanent scarring on a person's body, of a random coloration but usually blueish-violet.
The Weeve & Leylines
Simply put, the Weeve is the primary and predominant way raw magic is accessed. The Weeve is a system of invisible "rainbow-colored veins" that pulse and flow throughout the world, touching almost every corner of existence with the exception of dead-magic zones. The Weave is owned and controlled by no one, but the one who gave the ability to access it to mortals, was Rhy'Thm.
Among the Weeve are clumps of concentrated magic called, Leylines. These Leylines are the strongest sections of the Weave, and the many branches that sprout from them are what spellcasters (mostly arcane) use for their spells and magic. Leyline Confluxes are junctions where many of the branches meet, and are the densest parts of the Leylines. Confluxes are essentially the roots of Leylines, and the densest areas of the Weave. Should a spellcaster ever gain the knowledge and sight to see a Leyline Conflux and then attempt to draw magic from it, death would be a merciful end to them.
Essentially, the denser a Leyline's branch is, the more potent and dangerous the Magic within it. The Leylines also affect the barriers between the planes of existence, and they move and change size based on the time of year and celestial alignments. Notably, they are thinnest oX tXe XXXd oX evXXy XXXXX.