The core is the magical center of an individual. Every being has a core, although for many species on the Material Plane, such as most animals, it remains dormant for their lifetimes. A human's core will awaken at a certain age, usually in the second half of development (13-26), assuming they have an aura significantly large enough. Sorcerers are humans whose cores were awake at birth, and for whom mana manipulation was a skill they learned like walking. Metaphysical beings are always born with open cores. Every core tends towards one aspect of mana; for humans, this could be any primary aspect. It is somewhat genetic, but complex enough that there's never any guarantee what a child's core may be. For metaphysical beings, one's core is entirely dependent on their species, and is usually the same as all other members of that species, with the exception of constructs and some fey creatures. For example, all infernals have shadowflame cores. Awakened cores will passively draw in mana from its surroundings. This is called mana absorption, or just absorption (measured in thaums, or xm). The speed at which this happens is dependent on the person's natural abilities, their experience casting spells, and the density of mana around them. Each core has a 'mana capacity,' which is the amount of mana it can hold at one time (measured in mana points, or mp). This tends to correlate directly with someone's potential power when it comes to spellcasting, as it allows for more spells of a higher complexity to be cast quickly. Metaphysical beings have singnificantly higher mana capacities and absorption rates compared to humans, on average. People with awakened cores can open and close their core to the world like a muscle, with more minute control developing over time. Absorption rate scales with how open someone's core is; it absorbs as fast as it can while the core is fully open, and doesn't absorb at all while the core is fully closed. One's sensitivity to magical residue is also porportional to how open the core is; with a fully open core, it is much easier to detect fainter traces of residue, and from much farther away. However, when one's core is open, they are much more vulnerable to magical attacks; Rose, with her shadow core, could likely by taken out with a single ight attack if she kept her core fully open. As such, spellcasters keep their cores shut during fights. This has the side effect that during a fight, neither spellcaster can recover mana from the environment, and once they run out of mana, they've basically lost.