Duncan Idaho is the only character who appears in all six of Frank Herbert's Dune novels - a feat made possible by the Tleilaxu art of growing gholas, cloned bodies restored from the cells of the dead. In the original Dune, Duncan is a loyal Atreides swordmaster who dies heroically defending Paul and Jessica during the Harkonnen attack. In each subsequent novel, a new Duncan ghola appears - each iteration carrying the memories and skills of the original, but shaped by the circumstances of his resurrection. Duncan becomes a recurring lens through which Herbert examines identity, loyalty, and what it means to be human when you have been remade countless times. By the final two novels, Duncan's accumulated experience across millennia makes him central to the resolution of the series.