"Los Cuentos de Dunk y Egg - Precuelas - 3 El Caballero Misterioso" by George R.R. Martin is a novella that forms part of the "A Knight of the Seven Kingdoms" collection, which serves as a prequel to Martin's renowned "A Song of Ice and Fire" series. This particular story revolves around the adventures of Ser Duncan the Bold, commonly referred to as Dunk, and his squire, Egg, who would later become King Aegon V Targaryen.