Channelers
Although the books contain many characters who can channel, the ability is actually rare in the population as a whole. Among those who do have the ability, most must be taught. Without instruction, a person with the ability to channel could go his or her entire life without ever channeling at all, or without even knowing he or she even had the ability to begin with. Generally those on the main continent find out when a member of the series' only formally-organized group of channelers, the Aes Sedai, visit their town on a recruiting trip. Aes Sedai visitors also search for the few channelers who are born with "the spark," an innate gift that will inevitably lead them to touch the Source. If left untrained, these gifted channelers often die without ever gaining control over their innate ability; the Aes Sedai estimate the mortality rate at 75% or more.
Those who survive, called "wilders" by the Aes Sedai, do not realize that they have channeled, only that "things happen" if they want them to. To aid in this self-deception, they often develop a "block," an instinctive self-preservation behavior that keeps them from channeling in all but exceptional circumstances. Known blocks include only being able to channel while angry, in the presence of men, with one's eyes closed, and so on. These blocks can be eventually overcome, but only after significant and sometimes drastic counseling. The trainee, Theodrin Dabei, who could only channel in the presence of men she felt strongly about, for instance, was broken of her block when Charel, the handsome young stableboy who had been attending her training sessions, revealed that "he" was actually the handsome young stableboy's twin sister Marel.
Channelers must first tap into the One Power before being able to channel it, and can "hold" the Power within themselves without using it; the feeling of accessing the Source is described as being "more alive than ever before," a powerful feeling of joy for women, or a feeling of "holding a river of frozen fire and burning ice" for men, as well as a significant increase of sensory acuity for both sexes. The "sweet" and addictive nature of the Power is problematic in itself, as drawing too much of it can kill the channeler, render them brain-dead, or — if they are relatively fortunate — "burn out" the ability to channel permanently.
Channelers can also be deliberately cut off from touching the Source by others, temporarily by means of shields woven of Spirit, or permanently; modern Aes Sedai call the latter process "stilling" when done to women and "gentling" when done to men, while historically it was called "severing" for either sex. Regardless of the circumstances, those who lose the ability permanently also tend to lose the will to live, and are often dead within a year. Very recently, Aes Sedai Nynaeve al'Meara and Asha'man Damer Flinn have (independently) discovered how to heal severing, but the process only works completely when the healer is of the opposite sex to the healed; when Nynaeve healed fellow Aes Sedai Siuan Sanche and Leane Sharif from their stillings, they were left with significantly reduced strength.
Channelers are not born equal: some are stronger in the Power and can handle larger quantities of it than others. Men and women, furthermore, are different in many regards when it comes to the One Power, as covered below.
Read more about this topic: One Power