Cleansing of saidin
From A Wheel of Time Wiki
The Cleansing of saidin was a cataclysmic event that occurred at the climax of Winter's Heart and was felt throughout the entire channeling world.
In Winter's Heart, Rand al'Thor made an extraordinary claim: he believed he had discovered how to cleanse the Dark One's 3000-year-old taint on saidin. While Rand was inside the redstone doorway ter'angreal, one of the questions he asked the Aelfinn was how to cleanse saidin. The answer to the question is never actually given, but it is known to be a riddle that Herid Fel said stated "sound principles, in both high philosophy and natural philosophy."
During the meeting of the Cairhienin rebellion, Rand is cut by Padan Fain with the ruby-hilted dagger, overlapping the wound on his side given to him by Ishamael during their fight over Falme. The two wounds seem to eliminate each other's taint and allows them both to finally heal. This seems to give Rand the idea of how to cleanse saidin.
Rand and Nynaeve al'Meara used the two most powerful sa'angreal ever made, the Choedan Kal, one buried in Cairhien and the other on Tremalking to funnel the taint into Shadar Logoth. The evil in Shadar Logoth, which was born out of pure hate for the Shadow and the Dark One, caused the taint to "slide" off of saidin and into the city, where the two forces annihilated each other. As of Books 10 and 11, it is believed that this process was entirely successful, although what it means for the Asha'man and other male channelers (not to mention the Red Ajah) remains to be seen.
During the cleansing a battle took place between the forces of light and the shadow. The forces of light under Cadsuane Melaidhrin split into several groups of Aes Sedai and Asha'man linked to be ready for the upcoming attack. The Aes Sedai Sarene Nemdahl and Corele Hovian linked with the Asha'man Damer Flinn, while Elza Penfell (who is secretly Black Ajah) and Merise Haindehl linked with Jahar Narishma (one of Merise's warders, wielding Callandor). Nesune Bihara, Beldeine Nyram and Daigian Moseneillin linked with Eben Hopwil. Verin Mathwin and Kumira linked with a Sea Folk Windfinder Shalon.
The forces of the Shadow consisted of Cyndane (formerly Lanfear), Demandred, Osan'gar (formerly Aginor, who we find out has been masquerading as Corlan Dashiva, an Asha'man), Moghedien, Graendal, and Aran'gar who was formely Balthamel and now is in a female body but channels saidin.
During the fight, Osan'gar, Kumira and Eben Hopwil are killed.
