List of Magical Limitations (This list may inspire a spell, or it may be rolled on to see which magic limitations are most popular in an indigenous world).
NOTE: My book is somewhere, and I'm not up to hunting for it right now so no numbers in this, and its off the top of my head.
1. Code of Behavior
For some magic, you have to stay within the confines of a code of behavior, or the magic leaves you. The stricter the code of behavior, the greater the bonus.
A. Paladins
B. Good Witches
C. Prophets
D. Good Kings
2. Those sensitive to magic can sense you. Ranges vary from on the same street to the same county, same state, same continent, same world, and same universe. A special category which is a separate bonus is nearby dimensions.
Thus Caitlin Saunders,verser, Demon Slayer, and former Accountant from Earth casts her spell of Disintegration against a Foul Minion of the Shadow. In a neighboring dimension, a Hellworld, the Demon Grz'lak'nik wakes up to the smell of Power, and starts to track the spoor with his Hellhounds.
A further limitation is that the smell of magic does not leave you immediately. While close physical proximity to the caster's once location is the typical default, again greater ranges are possible.
Grz'lak'nik arrives ten minutes later on Earth with his hounds cloaked in a veil of invisibility. His hounds pick up the spoor, and he spots the smear where a foolish Minion challenged a Demon-slayer. He cackles grimly. He believes in the virtue of ambush. Caitlin will not be so lucky later tonight as he stalks her.
3. You use the magic for an improper use, and you get punished.
4. Balance of elements magic--you cast a laser spell, and shortly there after, you're surrounded by shadow.
5. The traditional time, body involvement, items, and speech.
6. Certain languages get a bonus. While the use of any foreign language gains a bonus, the use of certain languages gains a larger bonus. Thus Spanish will benefit the native English speaker, but writing in Runic will be more beneficial, and speaking in Ancient Sumerian even more so.
Any language that has a status as a 'Tongue of the Angels' or 'Language of the Gods' has an even higher bonus.
7. For some magics, every use of magic reduces the amount of magic in the world. The proper expression of this is by the Arch-Magi Newton in the Second Law of Magicodynamics which states "All magical processes tend toward maximum disorder given time."
8. For others, each magi only has a certain amount of power. This is a physical limit. Magic learned under this school has a maximum usage number which is the typical set-up for a verser character (or my suggestion of the same).
Jacob Winters, Verser, Space Fighter Pilot, and former Video Gamer on Earth has learned the Sunbolt spell. He knows that he can cast it ten times in his quasi-immortal life. He's already used it four times, and he's facing off against a difficult Vampire named Gavin. He wonders to himself if this is the time to use it the fifth time...
A more difficult way to utilize this is to say there is a limited amount of magic in the world, and each user uses up some of it. This can be visualized better, perhaps, or at least more concretely, with the Mana needed for magic in "The Magic Goes Away" by Pournelle and Niven or the way that 'Defilers' drain life energy from plants and kill a circle of Earth about themselves when they cast spells in the Dark Sun setting.
9. Magic has an altering effect. For some types of magic, its toward evil which is the more commonly understood effect. For others, its toward good, and it makes the character unearthly. This is seen in C.S. Lewis's The Space Trilogy where the hero Ransom by Book Three is not completely of Earth anymore. And for others like the Mythos, the thin shell of sanity may be broken by the revelation of things Man Was Not Meant to Know (although its not certain Lovecraft meant that for everyone...for some of his characters might have survived just fine mentally, but with the difficulty of being eaten they did not prove that to be the case).
10. One effect is the gaining of things that are personal. This goes several directions at once. Certain magics, such as Voodoo, require personal items to make the spell. Others require the True Name of the target. The True Name can be one of two things--an innate name that something has, perhaps gifted to it by Adam when that something was nameless, or by some other Namer. Or it can be a secret name which is held closely.
11. Mana is a magic power field which may be gathered. There are various techniques for this gathering. A large number of spells require mana to be cast, and another huge amount require mana to spread the effect of the spell over a large area. Effectively in Multiverser terms, this is the creation of a spell that enables the later casting of another spell. In some universes, the mana may be held in an item. In others, it is gathered by will at the last moment, and then the spell is cast.
12. Some magic is Just Plain Unnatural, and so the usage of magic always rebounds to the detriment of the user.
Jonas Majeerle, verser, AC Tech, and Apprentice Mage opened the Black Book of Forbidden Spells while his master was out. He cast the first spell of entertainment and enjoyed a fine repast with beautiful waitresses, and the ghosts of famous men to converse with. Then he got up, and felt sick to his stomach.
He had a stomach flu.
Later as he ventured to the latrine, he tripped and fell down the hill.
Still later, he came in to see his master who was very angry with him. Inexplicably, he had forgotten to put up the Forbidden Book, and his master was aware of what he had done.
A bit humorous, but it gets the idea across. This is not 'no benefit to self'. Instead this is 'Magic is an aberration, and Nature hates it.'
13. No magic may be cast that is solely of benefit to yourself. You may cast a spell to destroy a demon because demons are a threat to one and all. You may not cast a spell to turn lead into gold to pay for your tab at the inn. If you do, you will find the Universe is messing with you....like having all the gold you touch turn to lead for the next week.
A more extreme version of this would only allow you to spell the demon if he was clearly a threat to another in the immediate future.
14. Roles must be respected: This is typically holy magic. The Prophet may not call down fire upon the Demon except in certain specific circumstances. Perhaps if the Demon manifests itself in its Hunting Form, a material killing machine, or if the Demon has been thrice rebuked by the Innocent, and it decides that instead of tempting the Innocent, that he will take the Innocent's cat hostage, then the Demon has stepped over his own boundaries, and may be dealt with by any means neccessary.
This is more common in worlds with strong codes of behavior and high magic, and potentially archetypical patterns are commonplace. It is a form of Armed Truce between the Host of Heaven and the Forces of Evil.
15. As Wodium says:
You can have Wild Magic which is not under the control of the user directly. Cast the spell, and then roll a GE roll. '21' or higher, and roughly what the player wanted, occurred. '27' or better, and something better occurred.
As a further wrinkle, you can have Wild Magic which activates potentially when the character is stressed.
Another wrinkle, mentioned by the Champions game is the idea...
You wake up in the morning...your hands are sore....your superhero costume is bloody...you don't remember anything....you see on the news....'ten gangsters bloodily dismembered last night in one of the most brutal....'.
And then there's Bink of Spell for Chameleon who has a magic talent which prevents him from being harmed. But he doesn't know how its going to operate. For this, you create a specified aim, and when certain conditions are met, the magic fires up...and goes off if the roll is successful, and the method the magic chooses is up to the referee's discretion.
Wodium, I'd be interested in seeing your 'Werewolf' post if you can come up with it.
Eric