The maesters are an order of scholars, healers, postmen, and scientists who are trained at a school called the Citadel. House Hightower was integral in the Citadel’s foundation, and continues to patronize the order. As advisers to the Westerosi nobility, the maesters have largely supplanted the Alchemists’ Guild. They are sometimes called “the knights of the mind.
The maesters are scholars, scientists, learned advisors to the nobility, and occasionally pseudo-religious researchers in the occult. Males of any age may begin training as a maester; females are not permitted to study or join the order. Noble families in Westeros sometimes send their younger sons to the Citadel. A bastard may study at the Citadel and become a maester. The maesters, like the brothers of the Night’s Watch, are considered to be servants of Westeros and all its people and in theory have no political allegiance. After finishing his course of study, a maester is assigned to a castle, keep or other holding, and is loyal to the people of that place as a mentor, healer and adviser, regardless of changes in control of that holding. To this end a man who earns his chain is stripped of his family name and from that time on is known only by his title and first name. In practice some maesters hold over old allegiances and loyalties.