— Moiraine Damodred
Balefire is a weapon of the One Power usable by both male and female channelers. Its widespread use during the War of Power began to cause the Pattern to unravel, and it was subsequently banned from use by all wielders of the One Power.
When a target is struck with balefire, its thread in the pattern is destroyed, in an amount proportional to the power of the balefire strike. This translates to the target's existence being completely erased, chronologically in reverse. For example, should an Aes Sedai use balefire on an attacking bandit, the bandit's action of attacking the Aes Sedai and anything leading up to the action of the attack would be erased; this would be determined by the power of the balefire attack. The stronger the balefire, the further back in time the object in question will be burned from the pattern. This can have serious consequences on the pattern; the use of an extremely powerful blast of balefire to destroy a great number of lives at once has been shown to produce an effect referred to as a "balescream," the sound of the Pattern itself groaning under the strain of rearranging itself around such a large gap. An interesting side effect of using balefire is that anyone that causes the "reversal" of time will still remember all the events that were undone as if they had actually happened even if the effects themselves no longer exist.
Examples of useEdit
During the War of the Shadow, the use of balefire had a horrible effect on the pattern. Whole cities were burned out of existence and the pattern was almost destroyed before both sides decided not to use it anymore.
Balefire can even bring people back from the dead, or rather, prevent them from dying in the first place; both Aviendha and Matrim Cauthon were brought back to life when Rahvin was hit by balefire with enough force to undo the attack that caused their deaths. In another instance, Mat was saved when the Darkhounds that attacked him were burned away to the point before injuring him.
The Dark One is unable to resurrect any person who is killed by balefire, mentioning himself that he is not capable of "stepping outside of Time." As balefire technically causes a person to die in the past, it is assumed that the Dark One can only resurrect someone within a certain time-span, with balefire exceeding that limit. Another possibility is that due to the nature of the wheel, when a person dies, their thread does not end, but is simply set aside until it is used again/reincarnated as another person. Balefire burns the thread meaning that the thread can no longer be used in the Pattern's weave.
In terms of defending against it, balefire appears to be unblockable by any other weaves of the One Power. Cuendillar is the only substance known to withstand balefire's effects, but whether it is capable of blocking or deflecting it is unknown. Callandor, while infused with the Power, was observed on one occasion to have the ability to part a stream of balefire and it is suspected that the crystal sa'angreal is made of a type of cuendillar. The only time the One Power has prevented balefire from reaching its target was during Rand's duel with Sammael: Rand and Moridin's balefire crossed paths, forming an unexplained link between them. These two instances are the only known occurrences of balefire being either blocked or diverted in the waking world. In Tel'aran'rhiod, Perrin is able to block balefire with the palm of his hand, dismissing it as "meaningless."
Typically, when struck with balefire, the target's colors will reverse (a Halfman will appear as white clothes on a black body instead of black clothes on a white body), and the object will fade away. When Rahvin was struck with a very powerful bolt however, he simply vanished without the typical scenario.
In order for a channeler to create balefire, he or she must be very strong in the Power. Moraine admits to only barely being able to form the weave yet at the time she was among the strongest living Aes Sedai. There is at least one ter'angreal capable of producing balefire, stolen from the White Tower by Liandrin's Group of Black Sisters, allowing this inconvenience to be circumvented, though they are almost impossible to control.
During the Last Battle, the forces of the Shadow were ordered to pick up usage of balefire again, which was used frivolously and recklessly upon several battlefields, particularly upon the Field of Merrilor, to the point where existence itself nearly unraveled, much like in the war of the previous Age. Then-Amyrlin Seat, Egwene al'Vere, found, as her last act, a counter-weave of sorts; it patched up the cracks in the land and turned crystalline those who had given themselves to the Shadow. Egwene named it the Flame of Tar Valon.