Scarce magic

Main concept: Magic is keep secret because it is a limited resource.

Magic is a byproduct of complex systems, a natural setting like a cave complex or a forest crates a pool of magic that can be drawn upon, artificial systems like a city or a society also create such pools.

Systems created by man produce magic quicker then natural ones, but natural one are larger in size and have a correspondingly larger pool of magic.

Pools of magic also grow in size with age, a older forest or city has more magic available then a younger one.

The refreshment of pools of magic goes quicker with the activity of living things in it, so a old cave system might have a huge pool of magic, but due to the lack of life in it, it takes a long time to refill.

Mages draw on the pools of magic available to them and try to keep trespassers from poaching their territories, keeping things secret means less rivals.

Naturals: Magic users who draw on magic reserve by innate abilities.

Weres.
Naturals who draw on the magic of a wilderness area, shape changing is easiest way to draw on magic along with increased strength and health, seldom bother to learn other magics.
Very territorial, stories of people being bitten by a werewolf and surviving only to become a wolf is result of local were trying to take out a emerging rival just before they learn how to change shape.
Full moon means more activity at night in area allowing quicker refreshment of magic pool, best time to change shape knowing magic will be wasted otherwise.

Shaman.
A sensitive who combined his mind with a magic pool to create a spirit that is a combination of everything which has contributed to that pool and the shaman himself. Shaman can lead ritual to refresh a pool or use the spirit to direct their magic without formal learning in magic. Spirits linger long after the shaman is gone, but seldom act on their own.
Most old world cities have a spirit, but new world cities either opposed all attempts to create one or have cleansed away all such spirit while they were still weak.

Ghouls.
A natural who harvest lingering magic from dead bodies, the older the body the easier it is to free up the magic. Necromancers are magicians who learn how to do the same with rituals rather then natural talent.

Vampires.
Created from death magic to harvest magic from the living. Nosferatu get more magic by inspiring negative emotions like fear and despair, while succubae get more from positive feeling like arousal and joy.

Powers:
Independent spirits who draw on a pool of magic created by belief in their existence. Demons, the fair folk, saints. Most of the benevolent ones have agreed to pass on their magic to the Chantry, a alliance of religious magicians who fight against the darker powers.

Some powers act like gods or patrons for voodou priests and witches, doing magic on their part in return for promoting belief in them, but such request often take long rituals to grant and the more requests a power gets the less likely they are to respond, making even magic users keep quiet or more difficult to do then they really are to discourage rivals.

Magicians:

Bards are magicians who learn to use the magic they drawn the pools of magic created from audiences
Such pools are relatively weak and small but can be created with a short term effort and are hard to poach.

The Ministry.
The secret society that rules most of the western world, draw on pools of magic created by bureaucracies and government, the more complex and time consuming the better. Every city has one and they use their magic for both their personal benefits and protecting their cities.

Secret societies.
Think free masons, complex rituals, organized group, and all to create a small pool of magic for the higher ups to use. Also, independent ministers, boy scout leaders, and such. Not all of them, just some.

Independents:
Magicians who draw on the power of lesser natures, a shopping mall, a large park, a corporation.

Due to the nature of magic, complexity means power, a ritual with chalk drawing on the floor, chanting, candles, several assistants and the burning of offering draws less from the available pool of magic then just drawing on raw energy and blasting someone with it, such complexities also serve as a kind of combination lock to keep outsiders from drawing on someone else pool of magic.

Feedback.
The complexities of magic goes both ways, a forest to empowers a bunch of were wolves with violent natures means local animals are hostile and magic drawn from the forest will fill the magician using it with a urge to use it in violent ways. A shaman calling up a spirit of the forest will find it hostile and shaped like a wolf.

The Pact:
A five hundred year plus old agreement to keep the existence of magic a secret, Marshals are the enforcers of the pact, drawing on a pool of magic created by the existence of the pact itself and fed into by organizations like the ministry. Marshals aren’t supposes to care about right and wrong, just in covering up evidence of the supernatural and eliminated dangers to the pact. Marshals are often spread pretty thin so they will often suborn independents and other groups who have endangered the pact into acting as their agents at some future time in return for not being killed or other wise punished.

Human sacrifice.
All the innate magic in someone become death magic as they die, dangerous stuff it take a trained necromancer to use, and they can just wait for people to die on their own, why bother killing someone. A power can take death magic by way of a sacrificial ritual and feed it back to a magician cleansed of the death trait, but the greedy bugger will probably keep most of it for himself. A trained magician can voluntary give all their remaining magic to someone else at the time of their death, free and clear, but most will use it to shape one last spell, with to curse their enemies or pass on a last message to their loved ones.

Ghosts.
Shaman, even those who never knew they were shaman, often create ghosts of them selves on the moment of their deaths, such spirit linger for so long as their magic last, unless they can tap into the sprit of the area and leech of it’s magic. Due to feed back such a haunted area take on a tinge of death magic which affect it and everyone in it.

Tricksters and marauders.
It is possible to steal away magic by weakening the pool which hold its, burning down part of a forest, disrupting the smooth operations of a city, etc.