HOW MAGIC WORKS: Magic, depending on skill level, can be limited to minor floating spells to necromancy. Magic requires plenty of energy, and depending on the difficulty of the spell, it can either be done without breaking a sweat or the mage can die. Those of a certain profession usually don't stray from that profession, as they've typically dedicated their whole life to it. (Like biologists, dermatologists, zoologists, etc.) The limit for the amount of things a mage can be is two (like witch and sorcerer | Warlock and alchemist) MAGE -- Person born with magic WITCHES -- Magic doctors WIZARDS -- Magic scientists ARTIFICERS -- Magic engineers ALCHEMISTS -- Magic chemists SORCERERS -- Magic real-time life editors NECROMANCERS -- Magic reverse coroner WARLOCKS -- Magic debtor (doesn't have to have been born a mage as they made a deal with/got cursed by a magical being that gave them powers) CLERIC -- Magic priest (doesn't have to have been born a mage as they get their powers from their god) SPELLS: I'm not listing all of the spells. As long as it's something small (make bug float, summon a small puddle of water, make someone a bit happy), then almost anyone can do it. Anything larger than that typically requires some sort of schooling/equivalent of multiple doctorates (make castle float, summon flood, cause a person to feel paramount rage).
