10 rules of magic.
1.Magic cannot Improve stats, even temporarily. Magic can be used to cripple or lower stats (though the ability to restore them should always remain because restoring to normal isn't improving) but it can't be used to boost stats. It can, however, be used to avoid saves. For instance, say someone wants to lift a heavy object. They could use magic to aid them in various ways (make the object lighter, make themselves stronger, have the magic lift with them, etc) and this would lower the difficulty of the action to the point where a save wouldn't be needed. But it would NOT increase their STR number.
2. Cumulative effects cannot exceed level maximum effects. This is a little hard to explain but think of it like this: If I had a knife and used a spell "Sharpen" on it, then the knife would get sharper. But what happens if I do that 10 times? Could I make an infinitely sharp knife given enough time and patience? The answer is no, because that shit could break the game in minutes as some smartass player turns a firecracker into a nuclear bomb. The limitation on the effects of cumulative spells is the casting character's wizard level. Eg, if a character with wizard level 3 tries to sharpen the knife, he can never get it above the sharpness that a 3 strength spell would confer because a 3 strength spell is the highest he can cast. So if he said "sharpen" twice and got 1 on both strength rolls, it would have a sharpness equivalent to a single 2 strength spell. If he said it three times and got 1 each time, then it would have a sharpness equivalent to a single 3 strength spell. If he said it 10 times and got any combination of 1's, 2's, and 3's, then it still only has sharpness equivalent to a 3 strength spell because that's the max he can do.
3. The number of simultaneous summons/mind controlled beings/ magical constructs etc. must be less than or equal to the wizard level of the controlling person. And each controlled NPC reduces the user's mind points by 1 so long as it is under his control. For example, if a wizard of level 5 and 10 mind points summoned up 4 skeletons, then his mind would effectively be 6 so long as they remained summoned. These mind points instantly return to their user if the summon is disbanded or destroyed. Magically created weapons, armor, and objects count towards this total too, as do "enchantments". So if you summon yourself a sword out of thin air, it takes a mind point to keep it around; and similarly if you make it so that your spear strikes with the power of lightning every time you strike or just make it far sharper than usual, that will take 1 mind to keep active as well. The mind point “taken” is the one used to create the spell, so if you have 10 mind and summon a skeleton, you drop to 9 mind, because the point is expended to create the spell and then remains gone while the spell is active.
4. No summoned creature can use magic. A summoned elemental might be able to shoot flames or wind or water or something but nothing beyond that.
5. No cloning yourself or others. Or, if you really want to let them, make sure the clone is an NPC and has its own desires. Also, killing it won't count as killing a wizard.
6. No generating currency or valuable items for the purposes of selling. Considering the prevalence of magic in this world, you can be damn sure that any store owner is gonna have methods of checking that those gold coins you're handing them aren't transmuted lead or just conjured up out of nowhere. And they will be very unhappy if they find out you're trying to scam them.
7. Transforming yourself, in whole or in part, is possible, but requires you to expend one mind point each turn while in combat. If not in combat, assume it drains 1 mind point every 5 minutes or so. These transformations can affect your abilities (fly with wings for example), alter check requirements, and make you deal more damage or have natural armor, but they don't change your stats.
8. Overly vague or expansive spells will always fail. Something like "Win the lottery" or "I become king" cannot succeed regardless of the power the spell has.
9. No resurrecting player characters. Raising the dead is fine but treat them as any other summon; No magic, requires mind points to keep raised.
10. If you do something that breaks the game, I will drop bricks on your head from outer space until you stop or resemble a pancake. Whichever comes first.