Balefire

Balefire is the most strongest weapon usable with One Power, in a sort. It appears as very bright bar of "liquid fire" when shot. When it hits non-living (doesn't have soul is the definition, I believe) target such as wall or rock, it makes a BF-sized hole, but when it hits living target, it removes the target from the past, cancelling whatever that target had done in between, changing world into what it might have been if the person was gone.

So, A meets B, A kills B, C balefires A so hard it gets cancelled to the beginning => A is dead, B isn't.

<IMO>It is notable that while this definition of BF is functional, actual use of BF in books seems to be incoherent and occasionally self-contradicting and thus couldn't exist.</IMO>

Balefire was rediscovered during War of the Shadow and abused to insane points, completely wiping out complete cities before all sides agreed not to use it (it came close to actually unraveling the Pattern, whatever that means). Its use has been banned ever since, though some Aes Sedai (ie. Moiraine Damodred) seem to think those rules don't apply to them.

A fire that is prepared, and lot for magical or religious reasons, usually outdoors. Balefires are a traditionally used during Wiccan rituals for Yule, Beltane and Midsummer.

A brief summary of how time works in WoT:
Think of a spinning wheel/loom, spinning threads to make fabric. In the WoT universe, each thread represents a person. As people affect events, their threads change, along with other threads affected. These shapes that the threads take are known as the Pattern. In some cases, a person or group of people can affect other threads to an extreme level, drawing them into a pattern known as The Lace of Ages. People capable of causing such great changes in the Pattern are known as ta'veren.

But I digress.
In any event, balefire is capable of 'burning' a selected thread/person out of the pattern, actually destroying their existence before the destruction even occurs. Such destruction can be likened to pulling threads out of an article of clothing, eventually weakening the weave until the cloth falls apart.

Bale"fire` (?), n. [AS. bljr the fire of the uneral pile; bl fire, flame (akin to Icel. bal, OSlav. bl, white, Gr. bright, white, Skr. bhala brightness) + fr, E. fire.]

A signal fire; an alarm fire.

Sweet Teviot! on thy silver tide The glaring balefires blaze no more. Sir W. Scott.

© Webster 1913.