Magic is a real, tangible force in The Dark Mod setting, although no one agrees on where it comes from. Some believe it to be a natural force that comes from the earth itself, while others believe it comes from interaction with evil spirits or pagan gods. Most dramatic magical effects are relatively rare, and common people can't tell the difference between magic and electricity or other rare technology. Mages are those rare individuals who, through intensive study, learn to harness great amounts of magical power. They are generally feared and disliked by the rest of society, except when their help is needed.
Most people with a natural ability to use magic only develop the skill to do fairly easy things, like using tea leaves to tell fortunes, healing minor aches and pains, or creating small wards against rats or disease. With a little knowledge of alchemy or herbalism, these people can create successful potions or amulets. They are not considered Mages, however.
True Mages are those who have learned to channel magical energy to do powerful things like controlling the weather, or summoning the elements. Mages can learn to create illusions to mislead people or even summon evil creatures. Most of these things are highly illegal in The City. Learning these things requires access to ancient books or a teacher who already knows how to do them, so mages are quite rare in society.
Powerful magic spells like the above require large amounts of energy and concentration. Any slight mistake by the Mage can result in the magic going awry, with unpredictable (and usually highly dangerous) results. Mages do not use such spells without good cause, and thus powerful magical effects are rarely seen by most inhabitants of the city.
Story Idea: A miscast spell could result in a demon running wild through the local thieves' guild territory, or a powerful magic text being accidentally teleported deep underground. There are lots of opportunities for story plots here.
Creating magical potions and artifacts is less prone to unpredictable results, so mages tend to spend most of their time creating such things as ever-burning torches, love potions or protective amulets.
The Hermetic Order
The Hermetic Order is a loose organization of Mages in Bridgeport, headed by a Mage Council. This Council keeps its authority by maintaining complete control over the arcane books in the Order's Great Library. Only members of the Order are allowed access to these books, and without them a Mage cannot hope to improve their skills in any significant way. Copying or removing texts from the library is strictly prohibited so that the Council can retain their monopoly (they claim it is to ensure 'quality control' over magical texts and to guard against damage or theft).
Story Idea: The player could be hired by a foreign mage to steal a text from the Hermetic Library, but first he needs to somehow steal a wizard's talisman to gain entry (see below).
If the Council learns of arcane texts in the city that are owned independently (foreign mages or those who have discovered them in ancient ruins), the owner (if a mage) is 'invited' to join the Order and turn over the text. If they refuse, they are blacklisted. If the owner is not a mage, then the book will be either purchased or confiscated, "for reasons of safety".
Mages are forbidden from taking civic positions, but the Hermetic Order does have some political influence in the city. Nobles and merchants looking to hire wizards must usually do so through the Order, and they know that 'donations' often seem to lead to streaks of good luck, like fair winds for their ships. The Council can also forbid members of the Order from working for a particular family, so if a noble offends the Order, they will find it difficult to hire magical aid. Members of the Mage Council (Archmages) socialize with minor aristocrats and the masters of significant guilds.
The Council uses its political favour to protect its members from persecution by the Church. They have to walk a fine line between protecting their members and directly opposing the Church, however. The Council investigates any wizard who may be causing problems in the city, and any wizard who displeases the Council risks being turned over to the Church as 'an example'.
The Order works hard to be seen as a harmless academic organization, no different than the Scriber's Guild. They donate magical lamps to the city and assist the Surgeon's Guild by providing them with healing potions. They frequently draw the wrath of irate merchants, however, who tend to blame the Mages for their own bad luck, or the good luck of their competition.
There are fewer than 50 registered Mages in the Hermetic Order (not counting apprentices). While many people are born with the talent to use magic, few of them achieve the knowledge and strength to pass the application tests of the Order. They must also be taught the "Wizard's Tongue"--the special language that books of magic are written in to keep their secrets from outsiders.
When a wizard passes the application test, they become an official member of the Order, and are given a talismen to identify them. These talismans are magically bonded to the Mage and are used as their pass to the secret rooms in the library. A talisman could be a staff, an amulet, a ring, or something else significant to the mage.
The Council rarely keeps tabs on what their members are doing, investigating only if there is a serious complaint. As long as they don't draw unwanted attention to the Order (like working illegal magic in the open), and don't go against the rare edicts of the Council (like not working for a particular noble house), Mages are free to do what they like.
Magic in the City
According to current Church law, it is illegal in the city to make a living through the use of magic. At certain times in history, all magical business had to be conducted secretly. Currently, however, the Church is unwilling to totally outlaw the use of magic, due to the high demand from the nobility for magical services and the difficulty in proving magical interference. It is also hard to draw the line between using a magic earth talisman to cure someone's disease and tying a bone of St. Andrew to someone's foot to cure gout. So instead of persecuting all magical use, they just make it very difficult for Mages to operate (like prostitution in most modern societies--it's not illegal to be a prostitute, it's just illegal to charge money for their service). Of course, lots of Mages sell their magical services, but it has to be done 'under the table'. Mages either sell on the black market (to people like our thief) or they manage to get a wealthy patron who supports them in return for their 'wise counsel' (since they're getting paid only as an advisor, they are free to cast helpful spells for their patron on the side).
Certain kinds of magic are not only illegal, but they are considered evil and can result in the Mage being arrested by the Builders as an enemy of the Church. Magic that tells the future, magic that manipulates the mind, or destroying property with magic are all considered major sins. Obviously summoning demons and evil spirits, or desecrating the dead are also on that list. Other magic, like healing, summoning rain, and making magic lamps, are all considered acceptable, as long as you don't openly charge money for them.
Mages know that if they have a powerful patron who really values them, they are less likely to be charged with heresy by the Builders (who don't want to risk a political fight with the nobility). These mages tend to dress in outlandish ways, carrying strange staffs and advertising their status as a mage to all. The rich clothing is almost like political armour, informing those around them that they have enough political protection to be safe from Builder persecution. The less powerful the protection a mage has, the more conservatively they tend to dress in public.
Mages without patrons often live in the pagan district, where they are more accepted. Pagans have no special love of sorcery, but they are more comfortable with magic in general and more accepting of those who are different.