from the Introduction:
To most seasoned roleplayers, Magic: the Gathering is a game that needs no introducing. It is a legend in its own right, beloved of nerds, cherished by dorks. Even those who have never played Magic: the Gathering are most likely familiar with it to some extent due to its popularity as a cultural meme. Honestly, it's pretty unlikely that you're reading this if you're not into the game or the mythos of M:tG.
However, despite the tremendous popularity and near-universal presence of Magic the world over, for some reason, the game has never been adapted into a Roleplaying Game or World Setting. The campaign setting supplement you're now reading is proof that I find this fact shocking, ridiculous, and in need of fixing.
from A Little About This Campaign Setting:
In the rare event that you're unfamiliar with Magic: the Gathering, this campaign setting needs some explaining. The worlds (yes, plural) of the Magic: the Gathering multiverse are notably and primarily High Fantasy in flavor, with sprinklings of Steampunk gadgetry, Gothic Horror beasties, and Samurai and Ninja jidaigeki. Classical Chinese Elementalism governs everything in the Magic multiverse in the form of five symbols (fire, water, etc.). Each symbol governs and influences multiple spheres of life, the universe, and everything, and are crucial to the atmosphere of Magic: the Gathering.