During the First Age, Dior was married to Nimloth and the two had three children: Eluréd, Elurín and Elwing. After his father was slain by the the dwarves who coveted the Nauglamir, Dior became King of Doriath as Thingol's only heir-apparent. There he and his wife lived in peace for sadly only a few years for when the Sons of Fëanor heard that a Silmaril was there they declared war on them.
Dior, along with Nimloth, Celegorm, Curufin, and Caranthir were slain by the Sons of Fëanor during the Sack of Menegroth to recapture the Silmaril he inherited from his parents. Dior's sons Eluréd and Elurín were captured during the assault and left to die in the woods of Doriath by the servants of Celegorm. However, his daughter Elwing escaped with the remnant of the Elves of Doriath to the Havens of Sirion, where she wedded Eärendil the Mariner and they together sought pardon and aid from the Valar.