Gurney Halleck was Warmaster for House Atreides during the reign of Leto Atreides I, and then his son Paul. Along with Thufir Hawat and Duncan Idaho, Halleck was one of Paul's principal teachers during his early years on Caladan. He was a ruthless, yet noble and romantic warrior of enormous talent. Described as "an ugly lump of a man", he was regarded the most loyal of friends to those he loved, and to those he hated there were few enemies more terrifying. A traditionalist and purist at heart, Gurney Halleck did not indulge in melange addiction or other methods to prolong human life.