From the introduction: The planes of Magic: the Gathering are diverse in their themes and mechanics, but a uniting force behind them is the idea of the color wheel. This is an attempt to adapt that to the rules of 5th edition Dungeons and Dragons. In this system, the players each take on the role of a legendary creature and as such, must select what color or colors that their character would find themselves aligned. Also, the use of the word "mage" comes from M:tG and is used to actually represent all player characters in this case. Even a fighter who has no "magic" to speak of would be considered a mage under these rules as they "draw their power" from their chosen color or colors.