Magic is endemic to the Greyhawk setting, and yet not well enumerated. The rules below seek to create investigation of those who employ magic, and the nature of magic itself in the setting.
Each magic tradition has its own way in which these powers are gained, and various sources for the powers. These are sometimes obvious, and other times need to be developed a bit. The nature of the method by which the powers are gained, however, will determine how to group magic powers. For instance, a particular book of magic will tend to focus on this or that sort of magic, and if it’s assumed that the character has studied this particular tome, then the character will have the abilities from that tome.
A player with a Magic keyword that assumes that it’s some deep tradition will give the player about 8 to 10 magic powers. These should be organized into the groups mentioned above… the spells from one book, or the powers given by an aspect of a deity, or the tasks that spirits can carry out for the character, etc.
Individual abilities are just the names, often vague in purpose before they are used.
Magic in Resolution
Magic is a “wildcard” in terms of category. If there is a category in which a die has not been specified, then Magic can be used to fill in. If the player has dice for every category, then magic can be substituted for one of the other dice.
Creating Situation Dice with Magic
Magic is often very much for creating situational advantages, and does so with relative ease. As such, when magic is used so, the GM may only turn two dice of the opposition dice into the target die (as opposed to the usual three).
Requirements for Magic
Magic is supernatural, and this means that using it is never without the potential for interesting consequences. If magic is used in a way that is contrary to the nature of the supernatural forces that spawn it, the GM will have a contest between the character and a difficulty based on how egregious the issue is. Failure will result in a reduction of all magic abilities by the damage amount.
Genrally speaking the character’s relationship with their magic will evolve over time, and depending on its sort, this will require any number of sorts of care and maintenance to keep functional.