I'm fairly new to this website and I've seen how amazingly creative you can all be and I was wondering if any of you people could potentially help me. Essentially a friend and me are rewriting a story we started years ago as little kids (it's terrible), it's set in a separate fantasy world, based semi around the medieval period twisting real world events or myths (i.e. the plague) to help with the plot.
It also has a magic system, unfortunately I have absolutely no clue how to further develop it.
The main premise I have is it being based around crystals and the user must have a crystal on them (necklaces, rings and staffs are all popular options - although other method ideas would be appreciated). Different crystals would have different properties (maybe allow different powers, although I don't want every character to be able to access every power) and I think maybe the size would effect the level of power (a reason to have a staff rather then a necklace). I think the crystals could also glow, potentially different colours if a character has multiple abilities they can channel through it.
The types of powers are the thing I'm most stuck about. Elemental powers and healing are all I really have at the moment, but I have no actual development on that (other then healers not being able to heal themselves, and healing potentially hurting them, I'm not entirely sure on that one). The other character also has "acid blood" but I'm not actually sure what it does, or if I'll even keep that power. Shape-shifting (currently the only form I have is a wolf) is also possible, but I have no downside to it as of yet.
Any development on the current ideas, or new ideas are both appreciated. Also feel free to scrap/change anything I mentioned. Thanks in advance.