As a former Linguistics major at a good university I feel compelled to mention that the term "magics" is perfectly grammatically appropriate to refer to many different types of magic. It is an optional use of the plural that exists for many words. Fishes is another example. One fish can be either one single fish or one type of fish such as salmon. Many fishes refers to many different types of fish, such as a list like salmon, trout, cod and halibut. The word "magics" has the same use. You may talk about magic as in one spell, magic as in the magic of Wicca or many magics as in the magics of the world (which include Wiccan magic, Christian magic, Hindu magic, Chaos magic and many others).
Just to put things straight. Magics is perfectly fine for that usage.
Ok, my Linguist-nerd moment is over. Thanks.