There are only two things that limit what you can do with magic; the amount of power you have, and what you can understand. These are both fairly obvious; you cannot do something if you don't have enough power to do it, and if you can't understand something, you can't make yourself do it. This is true for everything, not just magic; if you can't understand algebra, there's no way you can solve a quadratic equation. If you are a one-hundred pound weakling, you can't lift a Mini over your head. (And I advise you not to try!)
But, apart from these two factors, there is no limit to what you can do with magic. You can move objects, start fires, affect peoples thoughts, or whatever else you may want to do.
There are people who will tell you that, as a human, you have only a limited amount of power available, and will need immense practice to become truly skilled. They'll tell you that to become truly powerfull, you need to become something other than human.
There is a small amount of truth in this, so I will cover it here. You are, I'm sure, familiar with most of the supernatural beings a human can become if he wishes. Most famous are the vampire and the werewolf, but all the mythological beings from folklore and fantasy tales are possible: fairies, goblins, angels, even unicorns.
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