There's a lot of stories with this basic concept, anywhere I can further my knowledge on the subject?
Hi, Little too broad a topic I'm afraid. Pick a culture from the time period and then study what they believed in. For Europe and the middle ages you're probably looking at alchemy, witches and demons. In the middle east it would be djinns and genies. Cheers.
If you want just a kind of general knowledge of medieval themed magic, just read fantasy books. But if you want real knowledge of medieval 'magic' then you gotta do some research, in which case google is your friend.
I would recommend reading some role playing games that make up systems for magic. A lot of people in the real (European) middle ages thought magic was just an illusion of the devil... That's not always as exciting as people who can really do magic things. I would recommend inventing a consistent system of magic for your own little universe. Or borrowing one if you don't need to worry about copyrights. A key concept though is consistency. If your wizards can all fly in the first chapter, then they shouldn't forget about this ability in the third.
Fairy tales and myths contain lots of examples of magic. For example, in ancient Nordic (Norse) mythology, sejd was a form of divination which involved getting into a trance through incantation or dancing. Songs could be used for magic, for example, to wake the dead and ask them questions. There were also magical runes. Sacrifices were used to gain the favour of the gods in battle or with the weather. There are also lots of old superstitions which can be used as a base for magic, from tricks to keep the fire burning in your hearth, to the belief that bad luck and illnesses were caused by curses laid by jealous people. With a little creativity, you can also base magic on general folk beliefs. For example, in the Northern European countries, people believed in small magical creatures living just beyond the normal world, like the helpful tomte, who cared for your crops and your animals if you treated him well, but sabotaged them if you upset him. These little creatures had magical powers of their own, and one of them could conceivably carry out magical tasks for your characters if appropriately threatened or bribed.
I am currently working on my magic system. It is without a doubt one of the harder things to flesh out. The novel I plan on writing doesn't exactly revolve around those who can cast (although who knows a book can change in the writing) but I still want a fully fleshed out system before getting into the writing. I am ticking boxes to get mine working. A, where does the magic originate from? B, how do the people interact with it? C, how does it work? How is a spell cast? D, what is its place in the world?
A) Different world, different laws of physics. B) You can either choose to create a world where magic is popular and accepted or you can choose a more medieval setting, where magic is discouraged. In the first case magic would be like technology to us, in the second, well, it's gonna be boring with the worshippers, the Inquisition etc... C) It might a conglomerate between a ritual and some inne forces in particular individual. D)See point B.