This volume examines the nature of aristocratic society in the Spanish kingdom of Le'on and Castile in the twelfth century. Drawing on an extensive range of original sources, many of them unpublished, it highlights the unrivalled wealth, status and power enjoyed by some members of the aristocracy. It also explores the multifarious roles that lay magnates were expected to fulfil: as family protectors, landlords and judges; as courtiers, diplomats and military commanders; and, not least, as patrons of the church.