Magick and the Medieval Mind
To the medieval mind, magic is not supernatural. It is a branch of natural philosophy, which is to say, science. Specifically, it is the study of the occult (in the original meaning - hidden) properties of things. As such, there is nothing inherently evil or satanic about the study or practice of magic; it is no different than the study of horses or the making of swords. To the medieval mind, penecillian would be a magic potion, because the ability to cure disease is not an obvious property of bread mold; it is a hidden, or occult property.
What magic is used to do is as variable as any other human activity; using magic to kill someone is no different, legally or morally, than using a knife. Causing harm, or interfering with someone's will (such as a love potion) is wrong, regardless of how it is done (and is a very serious crime in the Empire). Thus there are no legal restrictions on the use of magic as such, but magic as a tool to commit a crime is no different than any using any other tool.
The primary goal in the study of magic is the secret knowledge of all things, and of the world itself, and using that knowledge to impose the practitioner's will on the world around him (to force it to divulge even more secrets). This inquiry takes many forms, but most practitioners are studious and academic, and have little interest in the mundane world, or exerting political or other forms of influence on it. An interest in wealth is common, but usually only as a tool for their research, as the equipment and supplies for magical research can be very expensive.
Each practitioner develops his own methods, and these vary widely, from music to drugs to astrology, but always to the same effect: as an aid to focus the practitioner's will on the task at hand. The more tightly one can focus one's will, the more strongly the will can be imposed on the world. Some secondary methods do appear, as well. The cabbalist learns to store the effects of his magic in symbols, the mechanician is as adept at engineering as the occult, and alchemy is as much chemistry as magic. The "natural talent" is someone who has an inborn ability to focus their will on the external world without training or paraphernalia, and as such, are usually not very accomplished (though with experience, this can change).
Magic practitioners tend to fall in to two categories: the educated, professional practitioner, and the amateur, often regarded as a "hedge wizard" or "witch woman." The professional is usually well educated in all things, above average intelligence, and if not Lawful, at least well aware of the many ways in which one can be caught misusing magic (or any other form of power). There is a guild to regulate, if not magic, at least the magicians. The Magic Guild is more formally organized than most (though it is one of the few that freely accepts apprentices from outside families), and its members' skills (and wealth) make it very powerful. It exists (as do all guilds) to protect the interests of its members from outside malice, and this includes policing its own membership when necessary.
The amateur wizard if usually a commoner, uneducated, ignorant, superstitious, and usually not very bright. Their knowledge of magic is usually handed down from parent to child by oral tradition, and almost always imperfectly (and it usually seems to involve smearing oneself with feces or blood, or something even more disgusting). There are common beliefs in the occult properties of many things, and that these properties determine what a thing can be used for. Wolf's blood, for instance, used in a potion, is believed to imbue the drinker with courage and ferocity, and bear scat can be used to repel biting insects, or unwanted romantic advances. More educated practitioners know that these things work only because the hedge wizard believes they will, but work they often do.
Distinct from magic, per se, is necromancy. (Medievals used the term differently than the game as published, and as we use it today. What we would call necromancy, they would simply call grave robbing and desecration of a corpse, and the study of the occult (or hidden) properties of dead bodies. What they called necromancy, we would call demonology. This essay will rely on the medieval usage.) The summoning of demons uses magic, but the forces involved are supernatural, and it is inherently evil. Angels are subject only to God's will, not man's, and fallen angels, who have defied God's will, and exerted their own, lose this protection. Thus, any being that can be controlled by a summoner is, by definition, a demon, and, by definition, evil. Trafficking with demons is the most spiritually (and bodily) perilous activity known to man, and is universally condemned by all civilized people. Those convicted of such heresy are tortured until they repent their crimes against God, then immediately burned at the stake.
Demonology requires the careful practice of rigidly defined rituals, and every detail (and there are many) must be perfect. As a result, those who engage in it are, universally, in need of a high degree of education and literacy (as well as a lot of money). Furthermore, the tomes detailing these rituals, when found, are nearly always turned over to the nearest bishop to be destroyed. Some bishops have a reluctance to destroy any book, and many rationalize that there is nothing evil about the knowledge, only its practice, and knowing the rituals helps them (they feel) to recognize the warning signs that someone is engaging in the practice. There is also a school of thought that teaches that forcing a demon to perform good acts is morally defensible, but it is condemned by the Pope as heresy. So such books are not always destroyed. This means that it is a crime most often committed by churchmen, and occasionally by those with high noble patrons. Anyone else lacks the skills to survive long enough to complete the crime.