He prowled down an aisle of musty knickknacks. There was a trio of grim little statuettes carved from onyx, a wreath of silver thorns, a bejeweled goblet, a horned wolf skull. He took care not to touch any of them. Spike well knew the pitfalls of mucking around with mystical rubbish, even if the rest of Buffys Wanker Brigade didnt. To say the Witch was playing with fire would be a spectacular understatement. She was playing with bloody atom bombs, and when one of them finally went off, Spike doubted shed be the only one to get burned.
— From the Spike/Buffy fanfic The Fog of War, by Kitty Karnivore.
Well... the bad news is that this is a scroll of Locate Creature - which is a completely useless spell in the current situation. The good news is that I have absolutely no idea what I'm doing. Abra candelabra! Frippity fruppity frooj! Pottericus mimickus!
Reality is flexible and may be tampered with to some degree. It's easier when there are no Sleepers present to interfere with their disbelief, but even then the fabric of the world may be coaxed into a new pattern. The fibers of the Tapestry are loosely woven enough that they can incorporate some reweaving without ripping apart or snarling into knots. When the weaver moves too fast or tries to overthrow the pattern entirely and create a whole new design, however, the Tapestry fights back. Sometimes, this causes the weaver's shuttle to slip from her fingers; sometimes the loom breaks and smacks her in the face. That is Paradox.
—Mage: The Ascension - Core Rulebook (2nd edition)
Magic can go wrong in so many fascinating ways you have to spend six months at mage school copying out the rule book before they'll even teach you the wet dog spell. It's certainly possible to cast a spell with the fresh corpse of a man who's already said most of the words, because the magic stays stored up in his body; it's just that doing so is really, really stupid.
Magic is a living thing, inclined to all the same bloody-minded pettiness of other living things, and there are two things it really doesn't like: being cast by a dead guy (properly dead, not the inferior Dreadgrave brand) and being cast by an amateur.
The result of either was generally what we in the trade call a voyage to the cock-up peninsula." Meryl was attempting both. By the time she finished saying the word I had almost reached her, so I was around just in time to take a full-scale magical blowback right in the mush.
Spells can go wrong in many ways and for any number of reasons, but there are some relatively consistent symptoms caused by this. There are things in the cosmos and lurking in the deepest parts of the soul and darkest recesses of the mind that magic can release. The Winds can give form to anything within a mans heart or mind, his dreams and nightmares. Unfortunately, when a spell goes out of control or when it is tainted by Dark Magic, a window is often opened into the horror of a magic users subconscious, and the nightmares lurking there can achieve physical presence.
—Warhammer Fantasy Roleplay: Realms Of Magic (2nd ed)
Neither of you is advanced enough in your studies to understand this properly, but in time, you will learn that wielding magic means working with enormously powerful energies. And controlling these energies requires a calm and dispassionate mind. Use magic in anger and you will harm yourself much more quickly than you will harm your adversary. There are certain spells... if you lose control of them, they will change you. Consume you. Transform you into something not human, a niffin, a spirit of raw, uncontrolled magical energy.
—Dean Fogg, The Magicians