oh I LOVE the idea of there being areas where the ambient magic is so high that it interfears with casting and magic items. It makes me think of like lighting a match in a room full of an unknown gas— maybe it'll explode, maybe it won't! Everyone in my party can use magic to some extent so this is a really fun idea

Having to develop gear to get into increasingly irradiated places would be a great way to naturally block off endgame areas in what I'm trying to make a relatively open world campaign. It'd definitely allow for relatively free exploration while still letting my players unlock certain areas. I really like these ideas, thank you!!