Well that's what I like in magic
It has endless possibilities. My personal definition of magic is: "Magic is what makes miracles real."
To answer more precisely to your questions:
You can pretty much make the rules up yourself
as long as it doesn't conflict with anything I've written in contest description. Though I don't see anything that could conflict with it
If you want to do blood/disease magic I suggest that you create magic for Amnesia. She is a vampire and by battle profession she is a Dark mage that specializes on poisons, diseases, curses and like.
There are a few established dimensions connected to the world of Lavir, but dimensions are endless so you can create dimension magics if you like.
If by beyond you mean like from the world of dead then your character choice would be Kacy, she's a necromancer.