There are all different kinds of magic of course, but in fiction there are generally two:
- Machine Magic is usually part of a system where a certain outcome is more or less guaranteed as long as one faithfully repeats prescribed steps. Often this magic is imbued in an object that basically works like a piece of advanced technology. It may have to be “powered,” for example, or it may require specialized training to operate, but as long as the right conditions are met, the object and/or spell will produce basically the same result every time, or in the case of LitRPG, will do so with a defined probability. See Harry Potter or the fantasy of Jack Vance.
- Natural Magic (I’m tempted to call it Stochastic Magic) is not part of a system. Here, outcomes are fantastical and they happen, or don’t, for largely inexplicable reasons, like the acts of nature or the whims of the gods. Natural magic can include machine-like objects — The Mystical Mirror of Elmer which returns a loony vision to all who gaze into it — but such things, if present, are often corruptible and/or yield ambiguous or uncertain results, like the casting of lots or the cryptic warnings from the spirit in the crystal ball. See the works of Neil Gaiman.
Obviously there will be overlap, and there’s nothing that says a work of fiction has to conform to one or either of these, but generally speaking, most fantasy novels employ magic that emphasizes one of these two categories, even if it includes elements of the other — or something else entirely. The movie Dragonslayer is an artful example of a mixed approach that emphasizes the natural.
It’s probably clear that I generally prefer the latter, which necessarily puts more emphasis on character — although machine magic certainly doesn’t rule it out. Machine magic does, however, put more emphasis on action, which is why it’s used exclusively in the Doctor Strange movie, where, from the audience’s point of view, there is very little difference between Strange’s tricks and Tony Stark’s. (In the last Avengers film, Tony “conjures” a protective suit for Spider-man basically out of thin air.)
As a pure audiovisual narrative, film relies on what it can show, and machine magic is easier to show than natural magic because it follows deducible rules. You explain it simply by showing it in action. Machine magic is also easier to write when there is any kind of combat, which is why something like it is necessary in gaming: one can arbitrate a result very clearly. One simply follows the rules. To defeat the evil wizard, find and destroy his horcruxes.
Incidentally, this is why there are so many “chosen ones” in fantasy, young adult fantasy in particular. Since young adults are just exiting the home, where they were special, and entering the wider world, where they are not, there is a natural preoccupation with fitting in. A primary function of young adult literature, then, is to make the hero, and therefore the reader, seem special. If magic and magical objects work like machines, what’s to keep anyone from wielding them? A global restriction must therefore be introduced: only the chosen one can lift the magic hammer.
Natural magic is much trickier to write well. After all, if magic has no system, no rules, if it acts inexplicably to save your characters at the last second, then were they ever really in any danger?
In literary terms, this is deus ex machina, “the god from the machine.” Although the phrase is Latin, it comes from the Greek and refers to the penchant in Greek theater for dramatic tension to be resolved suddenly and inexplicably by the appearance of a god, whose portraying actor is propelled onto the stage by a machine — a crane or a riser — either to save the characters or to exact a terrible revenge.
For the Greeks, this was not a cheat. The narrative conventions of the time dictated that drama had to deliver a moral message — hubris leads to downfall, for example. Having illustrated that lesson through the plot and delivered the main character to his doom, the god appears as the agent of divine order.
These days, of course, we view such devices skeptically (in all genres but comedy, where one expects the absurd), which is why Gaiman’s “Ocean at the End of the Lane” ends so disappointingly. The goddess who was mortally wounded in the previous encounter inexplicably returns to full glory and saves the main character from the otherwise indestructible magic-eating monsters, leaving the reader with the impression he was never really in any danger at all.
Of course, characters aren’t only inexplicably saved by natural magic. They can also be inexplicably doomed by it. But if so, the story is probably a horror — where, even if the surviving characters discover the dream-monster’s secret weakness, it always roars back to life after the credits to torture more people in the sequel.
I said natural magic has no system, but that doesn’t mean it’s random. There is often an implied sympathy. In horror, for example, it’s the characters with some kind of moral failing who fall victim to the demon first. Even though there’s no “rule,” there is a reason why they can be eaten very easily while the others can fight back: the early victims are either too weak to stand alone and/or unwilling to stand with others.
In “Lord of the Rings,” only the innocent and noble Frodo can carry the One Ring. Everyone else is corrupted by its power — again, not because of a system that says as much. Simply because of the faults of their character.
This is how natural magic works well in fiction, by creating balance. Frodo can carry the ring by virtue of being innocent and noble, but in being burdened with it, he is plagued with both trauma and enemies, who seek him constantly. Indeed, the ring is constantly trying to betray him and using its power immediately brings his enemies to him.
This is how we avoid deus ex machina. An author simply has to balance any gain with a loss elsewhere. For example, she might “pay it forward” by having her novice wizard attempt a certain spell several times early in the book only to see it fail inexplicably each time, leaving the rest of the party to find another means of escape. Of course, it stands to reason that after so many tries, the hapless fool is bound to get it right sooner or later. So it is at the end, when all hope seems lost, the spell not only works but works more powerfully and wonderfully than anyone expected. The audience can accept the sudden, basically inexplicable success because it’s been bought on credit by the earlier failures in the same way that Frodo’s ability to carry the ring is matched by the torments it brings him.
This is “balancing” at the level of the character. One can also balance at the level of the book. Characters can fall inexplicably as long other are raised inexplicably as well. George R. R. Martin employs something like this in “A Song of Ice and Fire” (known widely as Game of Thrones). Because so many characters die basically at random, readers can accept the occasional inexplicable good fortune. It seems “fair” that if the one happens, the other will sometimes as well. Dramatic tension is preserved because in any encounter, readers will never know which way events will turn.
It’s important to note that this “balancing” doesn’t have to be 1:1. It’s not magical accounting, where every debit is matched by a credit — although you could write that if you wanted to. Natural magic is also not LitRPG, where a spell has a certain probability of success determined by the roll of a die.
But just because there’s no system doesn’t mean natural magic acts “without reason.” As an author, you must create a sense of balance or wholeness, which creates a sense of fairness, such that your readers are swept through the story naturally without stopping to tally merits and demerits incredulously. And to the degree you can write natural magic as an extension of your characters’ agency, of their unique weakness or potency as human beings, it can be much more personal and magical than, say, a final lunge to reach the amulet that anyone can use, or yet another story about a chosen one.