An example of a magic system

What secrets does this spell book contain (apparently polymorphing counterspells and potions). In my game, this might be vitally important to a PC to save an "innocent" (i.e. very wealthy) prince from a rival mage.

As a GM/DM/ST, I am ever fascinated by extrapolating the rules of a system, especially D&D's magic system. The reason I like taking D&D's assumptions about magic and fleshing them out is because, well, they are not very fleshed out at all. Like many fantasy settings, all D&D is really saying about how magic works is this "Priests/Paladins and Druids/Rangers Pray, Wizards wiggle their fingers and speak weird words, and sorcerers/warlocks just do it". That leave tons and tons of room to interpret the real reason of how magic works.

But why do I even bother explaining it? Because D&D, while not providing an explanation of magic, sort of demands one, at least in my games. Ever send your PCs on a quest to find the lost spellbook of a random archmage? Some of you may have.

Ever wonder why though? Why would a mage guild spend money, probably good money, hiring adventurers to get a book? Probably because it has some pretty awesome secrets of magic in it. But what secrets? When a PC, who probably doesn't even maintain contact with his mage buddies can crack open the 3.5 Spell Compendium and say "I learned this next," then what potency could a book have? I'll tell you, at least as far as my world is concerned.

How Magic works (in my homebrew)

In the beginning, my main Overdeity came in and created the material parts of the universe (he was bored). He married another overdeity, and she created life as they knew it then. The Overdeity had the power to manipulate everything he made: fire, gravity, rocks, space, time, etc. He did not grant that power to the people he created though.... at least not at first.

Mind you, those penitents had always been praying to him and the divine couples various children, and like any city councilmen or senator, they had decided to answer the prayers they liked best. That was essentially divine magic in its earliest form, and the "priests/paladins" of the life Deity were the earliest version of druids/rangers.

But the Overdiety wanted to give some of his followers a bit more responsibility and autonomy (just a bit), so he invented Arcane magic. Arcane means "understood by few; mysterious or secret."; as such, the Overdeity invented secret techniques, rituals, and formulae that would allow a person who did them correctly to do one very specific thing one time. I find a good analogy in Mortal Kombat: just as you must mash the keys a certain way to throw a fire ball in the game, you must do certain things to throw a fire ball in my homebrew.

However, clever Overdeity, could still cancel any spell he didn't like or strip power away from anyone at anytime. In fact, over time, some families of the Overdeity's vassals and administrators lost their abilities to do magic: hence magic is not available to everyone. The Overdeity also decided to create a sort of advancement system, thus creating a hierarchy of magic users. Since his wife invented this soul thingy (after she invented death, something he was not a fan of), he decided to have magic users tap that for energy. Their souls could only give so much energy at first, but like a muscle, they could be trained to give up more.

Unfortunately though, something bad happened, one of the Overdeity's sons got uppity and committed patricide. The Overdiety was the sole controller of magic, and had set up the system in mostly secrecy. Only a few deities knew most of the Overdeity's "passcodes" to power, and none knew them all.

Thus, for eons, deities and mortals alike have gone on grand quests to learn those secret gestures, weird words, rare materials, and vital information that makes them mages. Various Magical organizations have complied treatises on what rituals that have found, but are always hungry for more. Some mash spells together, or try to "guess the password" of certain spells, with disastrous results at times. And ever greedy for power, some learned magicians have destroyed books, spell cases, and whole libraries to monopolize those codes. Not to mention, the worshipers of the Overdeity's son despise everything that the Overdeity made, which sometimes means magic itself is blasphemy (besides, mages compete with priests for money and influence). Some whole categories of spells have been labeled "dark", and some dark beings have decided to capitalize on that designation, sponsoring dark magicians in their quest for more secrets. Still other deities create their own sort of "magic spells" within their domain, as do dragons and Fae have their own secrets (and may only give them up in exchange for something else...).

Magical scholars in my world thus have lots of work to do: decrypting ancient spellbooks, categorising spells, teaching them, keeping other spells secret, regulating the spells themselves, circumventing those same regulations, and finding new original sources. Magical scholars also try to find the common patterns between spells, since any ancient records of spells they have encountered may be incomplete: hence magical experimentation become necessary. That experimentation can lead to new spells being created, mostly by mashing two or three old spells together.

All this translates directly into 3.5 (and probably pathfinder) spell mechanics: the spells available in the books are probably the common knowledge spells: spells that have been passed from master to apprentice time and again.

Spell levels represent how much of a person's soul could be used for magic without suffering some consequences. Can mages in my game cast spells after they run out of slots then. Yes, if they have the right secrets.... which I can represent with different "versions" of spells, or metamagic feats, etc. Plus they can use a wand too. Otherwise though, a mages soul just cuts their mage off after a certain point. In fact, wizards have to do a sort of magical exercise to gain those new spell levels, which they probably due during their "rest" periods.

Souls also become very valuable, especially for dark mages and demons, because being able to use someone else's soul means you have a crap load of spell slots. Some of the bigger rituals that big bad evil guys do are merely spells that require more than one spell slot, and the PCs can do them all the same if they learn the spell. In fact, the aforementioned lost tome of Archmage McGuffin probably has rituals like that in there, and if he was so careful about his findings, he probably has spells of all sorts guarding his techniques.

What secrets does this mage hope to gain from this demon of the nine hells (maybe a cheaper version of Meteor Swarm, or a Teleport spell that never fails). What will be the price the mage has to pay for such knowledge (maybe his soul, so that the demon can sell in to a different mage...)

Interpreting arcane magic as a series of secret gestures and lost words also can create interesting plot hooks. Say that to cast a normal, standard mage school fire ball: you need a ruby cut to a certain shape. Not everyone is a jeweler though, so in order for a mage to blow something up he is probably going to have to buy the ruby. Guess who sells those rubies: that's right, the very university system that mage was taught at.

But lo, our PC mage heard a rumor that a certain long dead wizard never used a single gem in his life and cast fireballs just fine. If that PC gets a hold of those secrets, he can cast the same fireball cheaper. If those secrets got out though, the university systems racket would implode, and even mages don't like losing money.

That above adventure though implies that the same spell can have different versions, which allows for different flavors and cultures of mages to arise. Orc mages probably do their magic differently than elven mages, and those difference can lead to race warfare: the elves prohibit Orc magic in their lands because they believe that Orcs need blood for all their magic (which is only partially true). Different versions also play into magical duels: while in game terms the spell takes one action to cast, one action is approximately 3 seconds. What if one version of a spell, which only requires you to breathe a certain word onto a pile of ruby dust, takes 2 seconds to cast, as opposed to another version that requires you to gesture with a wand made from the femur of a fire giant that take 3 seconds to cast?

Spell set up this way can also create puzzle opportunities (puzzle box contains the book, the spell is hidden in a riddle), involve side quests (I need the egg of an Ostrich. WTF is an Ostrich?), and even create redeploying opportunities (BBEG is casting a spell that will slay my girlfriend! The only counterspell I know involves a human sacrifice....)

Can a fighter pick up a spell book and be able to cast fireballs? Maybe. Again, they need to have that "soul" training in order to tap the magic, or they need to use a tool. And why cant a god share/invent spells for his disciples? This thus creates excuses for eldritch knights, theurges, the like. Certain families of mages probably have proprietary spell books they keep to themselves, and thus magic enters politics and good old fashioned medieval feudal warfare.

DMs who enjoy crunch can take grant advantage of this interpretation, while DMs like myself can just rely on skill checks or seat of the pants judgements at times like this. In the case of the spell duel, I would tell my PC how their version of the spell works, and if they wanted to find a quicker version, they could roll Knowledge (Arcane) to see if they already know one, or roll gather information to see if they can find someone who knows a faster version (which probably wont come for free...)

I hope the DMs/GMs/STs find this post useful. I always encourage GMs to use their imagination and see if an interpretation of the rules yields interesting implications in the game world your playing in. Happy gaming!