Duncan is the son of Morpheus and Sorcha, his primary training and most of his life have been spent as a Custos. Before his arrival in Amber he had a close friend of Desirata as a ward and their time was primarily spent out in Shadow on Search for new candidates to be trained at the academies on Pathi. Typical of the Pathi Duncan keeps much of his past to himself, and what his goals and aims might be beyond his current duties is a mystery to most.

Duncan is currently the Archon of Iron, and once was the Ambassador to Rebma, as well as having served as the Custos to Duchess Lucretia of Mandrake and Prince Brand of Amber at various points since his arrival.