Prelude to Dune: House Atreides
A native to Geidi Prime, Duncan was taken into Harkonnen:House Harkonnen slavery at the age of just eight. He was frequently used by soldiers as 'prey' in hunts, usually eluding his captors longer than the other children. This earned him the ubiquitous honour of being personal prey for Glossu Rabban. Duncan was eager to participate, for the House Harkonnen na-Baron had killed his parents in front of his very eyes, and the young lad was seeking vengance.
During the hunt at a remote forest reserve, Duncan managed to outwit his pursuers by cutting out a tracking chip from his shoulder, using a dull knife he had been given for self defence. Using it as bait, he killed a Harkonnen soldier and stole his Lasgun, thus enabling him to kill several more soldiers. Shortly after, he escapes the planet by boarding a Heighliner bound for Caladan, home of Duke Paulus Atreides.
Upon recounting his tale to the Duke, Duncan is accepted into the household as a stableboy. However, during one of the Duke's routine bullfights, he is killed by a drugged Salusan Bull and Duncan is accused of Harkonnen treachery. The real perpetrator, of course, was the Duke's wife, Helena Atreides.
Prelude to Dune: House Harkonnen
Prelude to Dune: House Corrino
Duncan Idaho was in charge of the Atreides' military. Set with the difficult task of preparing the Atreides' arrival on Arrakis, he first saw the potential of the Fremen. During the Sardaukar attack on Arrakeen he died saving his young Duke.