The recipient of a discern spell, who must be a wizard of at least 5th level, is given the ability to know if another person has the potential to become a powerful wizard. Once cast, the discern spell is permanent (subject to a successful dispel magic spell). It functions continuously, as described later.
The discern spell is used to recruit members for various magical orders and schools of every alignment and ethic. The enspelled recruiter can learn if a person has the potential to become a powerful wizard simply by being within 10 feet of that person and interacting in a normal fashion with the candidate for two rounds.
The recruiter sees the potential for magic use in a candidate as a dim aura surrounding the subject. This aura does not really exist, so it is not detectable by other means, including true seeing. It is so dim that it cannot be perceived in bright light (such as direct sunlight). The aura is of constant strength, regardless of the potential of the candidate.
In short, a human, elf, or half-elf scanned by this spell registers favorably if the individual has an Intelligence of 15 or greater and scores of 6 or better in all other characteristics. A gnome registers favorably if the individual has the same and a Dexterity of at least 16.
Even if a positive result is obtained, the spell in no way guarantees that the person will become a great wizard (or even a wizard at all); it simply indicates potential based on intelligence, aptitude, and the will to achieve.
The Book of Black Circles stresses the fact that the spell is no more than a prediction; even a person who has the ability may opt not to become a wizard, quit before reaching a high level, or die before achieving greatness. The DM should use his judgment regarding who is highlighted by this spell's use.
The material component of the spell is a pinch of dust from a gem of seeing or eyes of minute seeing which have been powdered.
Notes: Very rare. Known to be in the Book of Black Circles. (Updated from Dragon Magazine.)