There is a TLDR section below for those who don't want to read the dialogue
„So, what is magic?“, young Fineos asked. „Well“, said Rhabea, trying to buy herself some time. „Magic is a lot of things.“ – „Yes, I know, but how does it work?“ – „It works in a lot of very different ways. There is not just one kind of magic.“ She knew what the other adult mages think of her and about her qualification as a mentor. „There are, at least, three different forms of magic I will tell you about, whilst we are together trying to make a mage out of you who will not kill himself out of stupidity.“ Sometimes, she thought they were right. „There is the Elwin’s Living Magic that can grow by itself. Then, there is the summoning magic sorcerers use, which needs quite some physical commitment to do its things.“ Rhabea was not sure if she understood the following part as much as she should, considering that she is about to teach someone to use difficult and dangerous things. „And then, there is the magic we can use. But even our magic doesn’t just work in one way. Nonetheless, we will focus on one way for today. Everything in our world is composed of tiny pieces we call atoms. They are composed of even smaller things, but you will understand this better when you actually learn how to cast magic.
Also, there are two kinds of magical energy in our world. One is everywhere around us. It seems like it's just flowing around and through everything. The other one is in us mages. That is what makes us different from peasants and kings alike.“ This took really long for her to get when she heard it first. „While the energy around us never seems to deplete, whenever you use your magical abilities your own energy will leave your body. To renew your magical energy you need to meditate or sleep. I will show that to you later on.“ It will take hours until she sees the essentials she forgot to tell the boy. „Now listen, this is really important. I will tell you how you can alter the world.“ For her it was always something she feels more than knowing or understanding it. „You can guide your magic out of your body. It will flow like a small river, always connected to you. Intuitively, you can let it out through your fingertips, but really every part of your body works equally. If, in the future, you will be more experienced,“ she never was, „you can guide it with your mind. But, also, using your fingers will help you a lot to get the hang of it. Now comes the hard part: With your magic, you can influence the magical energies of the world I talked about before. You can convince these energies to alter the atoms of objects and thus altering the objects themselves. You could make air more flammable or water to wine or even gold out of iron.“ – Fineos got quite an interested look on his face. „So why aren’t all mages rich and have castles out of gold?“ – She knew this question would come. It was one of her first questions, as well. „Because nature knows better what nature should be.“ Also, castles made of gold are typically not that stable and are prone to attract unwanted attention. „As soon as you stop fueling your spell with your energy, something known as natural balance will start to set it, reversing what you did as good as possible.“ Which killed or crippled more than one stupid mage who forgot about this rule. „Think about it like cooking soup. The soup is the object you want to alter, the fire is the magic of the world and the logs are your own energy. Without some wood the fire would instantly go out. But even then it would take a while until your soup is cold again.“
Fineos seemed lost in his thoughts for a few moments before he asked: „What about altering people? ... I mean, for healing purposes for example.“ That wasn’t his first thought and she knew it. But there was no need for lying to him. „In short: you can’t. We don’t really know why, but the human body seems to have a natural defense against intruding magical energies. But there is a way. If the recipient actively wants to let your magic flow into his body, you can do whatever ‚healing purposes‘ you have in mind. Though, at the moment he loses his trust in you, or his consciousness, your spell will got cut off and start to fade.“ The boy nodded absentminded trying to figure out the possibilities of his power.
Now, before I let you empathize with Fineos, consider a few things regarding the setting:
- It’s an earth-like medieval-tech fantasy world (because creatively has really small borders for me)
- My physics and chemistry levels are as low as mowed grass, so there is a high possibility that this idea might be really stupid; if so, please point it out
- Mages are pretty rare; it’s probably genetic and often comes with physical or mental disabilities (which leads to even fewer mages getting old enough to be mages, and stigmatises magical abilities for the general public)
- For your magic to have a visible effect you need to change quite a few atoms; this will take time (I don’t have a formula at the moment) but as you will get more experience you will be faster at altering the world, too
- Since this magic is based on atomic structures changing an atom to one close to it on the periodic table should be faster than changing it to one far away; that means changing gold to platinum (or even silver for that matter) should be generally easier and faster than changing it to iron, or vice versa
TLDR: There are two magical energies: one in the world around you, one in den mage itself. The own magic is some kind of catalyst for the world‘s energy. The world‘s energy consists of some sort of Ditto or stem cell atoms or maybe just protons and electrons (as said, I only know vaguely what I’m talking about). As a mage you can use those pink Ditto atoms to change the atoms of the desired object to whatever you like (with appropriate amount of Dittos and your own energy). When you cut your connection to the object, mother nature wakes up and starts to clean the mess you made to its natural state (if possible). Humans‘ (and possibly other animals‘) atoms can not be altered in any way, unless they want you to.
My Question: Can a magic system, as described above, work in said setting without breaking laws of physics or even breaking significantly more than pure physical strength could do? For example, it would be possible to alter parts of a stone pillar to something gaseous in room temperature, let it spread, then break the spell. In this way, the pillar could collapse due to its now missing parts. But this would be also possible for some beefy guy with a hammer. But I think to do the same with a mountain should be quite impossible (at least in a lifetime).
For Reference: The idea to this magic was sparked by Fullmetal Alchemist’s transmutation, but I think that was far too powerful and its theoretical restrictions felt more like loose guidelines to me.