The Aes Sedai are an ancient and powerful sisterhood of women who can channel the One Power - the fundamental force that drives the Wheel of Time. Based in the White Tower in Tar Valon, they are divided into seven Ajahs, each dedicated to a different purpose: the Red Ajah hunts male channellers, the Blue pursues justice and causes, the Green stands ready for the Last Battle, the Yellow heals, the White seeks philosophical truth, the Brown preserves knowledge, and the Grey mediates disputes. Aes Sedai are bound by the Three Oaths - they cannot speak a lie, cannot make a weapon for a man to kill with, and cannot use the Power as a weapon except in defence. These Oaths, spoken into a ter'angreal called the Oath Rod, physically shorten their lives. The organisation is led by the Amyrlin Seat, effectively a queen among the sisters, supported by the Hall of the Tower.