During the War of Power, two huge sa'angreal, one attuned to saidin and one to saidar, were constructed. The Choedan Kal were to be used to destroy the Shadow's forces and erect a barrier around Shayol Ghul until there was a safe method to permanently seal the Bore. The great sa'angreal were so powerful that using them required special ter'angreal access keys which were assembled in an area far removed. The access keys were lost and the Choedan Kal were never used (SaSG). <P> Though both statues are mostly buried, the tops are visible. The male statue stands near the village of Tremonsien and the female statue stands on the island of Tremalking. </P>

References#

• TEotW,Ch24 - Bayle Domon tells Rand about wonders he has seen including a giant hand holding a crystal sphere on the island of Tremalking.
• TGH,Ch20 - Rand, Loial, Hurin and Rand come upon an excavation of a giant statue near the Cairhien town of Tremonsien. Rand is nearly overcome by the pull of saidin.
• TGH,Ch31 - Verin knows about the giant statue in Cairhien and about its counterpart on Tremalking. She tells Rand that they are male and female sa'angreal. She says that only Elaida, Moiraine, Siuan and the three girls are strong enough to handle the female giant statue. Logain would be fried by the male giant statue.
• TSR,Ch9 - Lanfear tells Rand that, with the giant statues, they could challenge the Great Lord or the Creator.
• TSR,Ch58 - As Rand and Asmodean fight over the male control statue, Rand can sense the giant statue in Cairhien glowing. The power of the giant statue devastates Rhuidean and much of the surrounding country.
• TPoD,Ch1 - The Amayar of Tremalking have a prophecy involving the female statue on their island.
• WH,Ch11 - Rand gives the two access keys to Nynaeve and asks her to help him use the giant statues to cleanse the taint on saidin.
• WH,Ch13 - At Moridin's command, Cyndane tells the other Forsaken that Rand has the male and female access keys and plans to use the Choedan Kal to cleanse saidin.
• WH,Ch35 - At Shadar Logoth, Rand and Nynaeve use the access keys to activate the Choedan Kal and cleanse saidin.
• KoD,Ch22 - The female Choedan Kal on Tremalking melts after the cleansing. The Amayar see this as a sign that the Time of Illusions is over and they commit mass suicide.
• TGS,Ch47 - In the Stone of Tear, Rand wonders about Callandor. It is an inferior, flawed sa'angreal, so why is it mentioned in the Prophecies of the Dragon and the Choedan Kal are not?
• TGS,Ch50 - Atop Dragonmount, Rand almost uses the access key to destroy himself as Lews Therin did. He has his epiphany then drives the One Power back to the Choedan Kal and it explodes.