Magic on Corh is the manipulation of specific vital energies. Normally, this energy is called "vis", and is harnessed from blood, a substance rich in it, using a technique referred to as "occultism". Magic is not something that someone is born with, and indeed, magical education is the marker of many prestigious institutions of learning. While the base process is relatively simple, magic comes in a wide variety of forms, not all of which conform to the scientific occult paradigm.
All magic ultimately stems from vis, an intangible energy that composes the “natural heat” of a person. Vis collects in the blood over the duration of a person’s life, and that blood retains the energy of that heat even after being removed from the body, or after a person dies, and can then be used as fuel for magic. The "raw" form of vis has never been isolated, but substances high in vis (such as blood) have been shown to have innate healing properties. Manipulation of vis in blood is known as "bloodcraft", a term which encompasses occultism, evocation, alchemy, and all disciplines therein.
Vis is extracted through fire. It must be burnt out of the medium that contains it, thus becoming free energy able to be acted upon by the occultist’s will. In order to enact this will, an occultist must describe the effects that they wish to recreate in the Primaeval tongue, using their choice of spoken words or gestures, or a combination of both. These utterances in Primaeval are referred to by occultists as a "spell formula", a discreet set of descriptors in the Primaeval language that produces a specific, replicable effect. The traditional implement for occultists is a lamp lit not with oil, but with blood, usually hanging from a chain so as to be easily portable.
Occultists are known for their scientific view of magic. Occultists are responsible for the division of spells into five broad categories: apotropaism (defensive or warding magic), communion (magic that harnesses the "memory" of life within vis to obtain knowledge), malediction (curse magic), pyromancy (magic of flame and lightning), and restoration (healing magic). Ritualism is a pseudo-category of spells that require a long casting time, and occasionally specific vis-infused reagents. They are used to create effects that last for long periods of time, or that appear a great distance away from the mage.
Some magi choose instead to use the energy of their own blood before it has left their body, conjuring their will to burn through their blood and drawing magic from that. This discipline is known as “evocation”, and requires either intense fervor or deadly calm in order to avoid destroying one’s own life in the process. As such, most practitioners have a strong faith or other purpose of will, with the Flagellant Order of the Luminary Church being extremely powerful and feared examples of evokers.
While blood is the densest store of vis, vis does not exist only in blood; it also resides in the rest of the body, as well as in all other things of the natural world. The vast majority of these things (minerals, most plants, “mundane” animals such as sheep, cows, or wolves) do not possess enough to be useful to the human occultist. A handful of animals and plants have significantly higher quantities of vis, many of them having overt magical effects that they can control, consciously or not. Since it is less potent than blood, this vis must be heated to extreme temperatures in order to be extracted, unlike blood which can simply burn. Alchemists are suited to extracting it, as they possess specialised tools to do so, and can therefore work with the strange and arcane interactions between the vis of different species and mundane chemicals and tinctures.
Vis in blood can also be cultivated and refined through a simple but long alchemical process, producing a substance known as “quickblood”, which flows like water. Quickblood is what is normally bought, sold, and used in polite society, as its vis flows more freely than “quiet” blood extracted directly from the veins, and it has natural healing properties more pronounced than those of ordinary blood.
Further cultivation is practised by the Luminary Church through its sanguifers, people who take vows of seclusion and are given transfusions of quickblood by means of a “holy medium”, the identity of which is a closely-guarded secret of the church. The blood of these sanguifers resembles quickblood in many ways, but it has unique properties different to each individual, or rarely, each bloodline. Holy blood is used in church rituals, and occasionally used by church theurges.
The ability to manipulate vis also gives a mage the ability to manipulate spirits. All spirits, regardless of type, are drawn to vis. Anyone can use some spare blood to lure stray spirits in this way, but magi can perform rites to directly call spirits to them, and then bind them into service. These are two disciplines, known as conjuring and binding, respectively. Simply conjuring a spirit shackles it with weak magical "fetters", the technical term for the bond between a conjurer and their spirits, which enables a mage to command them for a short time, normally no more than a day. Occult scholars do not recommend that magi make use of spirit servants without binding them, an act that greatly strengthens the fetters. The fetters of bound spirits do not erode with time, only when they are being used to command the spirit, meaning that a bound spirit can remain indefinitely as long as the fetters aren't used up forcing the spirit to perform tasks.
Magi who make liberal use of unbound spirits, or even use vis to directly, verbally bargain with spirits for service rather than fettering them at all, are sometimes referred to as witches. Witchcraft is not permitted among most scholarly circles, since unbound spirits are considered dangerous by many occult institutions, but it is fairly common in rural settlements, where it often takes on spiritual or shamanistic undertones.
The ethics of fettering spirits is a subject of debate that still flares up every now and then in halls of academia and amongst hedge magi. Opinions vary greatly. The policy of the occultic lodge, the guild of occultists and alchemists of Yorving, is that spirits do not have morality or ways of thinking comparable to that of mortals, and so they are not subject to mortal considerations of ethics. Many witches believe that fettering spirits is cruel, especially those that refuse even to conjure. Others take a middle ground, binding spirits in return for a gift to the spirit or a task performed on its behalf.