Elfdag Eásternward was a Rohir child who lived in Rohan. He was the son of Elfmar, the Thane of Faldham, a settlement located within the Norcrofts of East Rohan. His grandfather was the Thane Elfhelm.
When the Rohirrim began to arm themselves in the armory of the Hornburg, Elfdag began to feel frightened as he eyed a large Beard Axe that was being held by an approaching older soldier. As the axe was lowered and handed to him, Elfdag looked up at the soldier, taking the axe with trepidation.
Elfdag later gave the axe to Hretel Hretelson before serving in the garrison above Helm's Gate during the Battle of Helm's Deep.
When a group of Uruk-hai attempted to breach the gate with a battering ram, Elfdag threw rocks down on them alongside Burnoth, son of Baldeg.
The next day, Elfdag was one of the soldiers that survived the onslaught after the battle was over. Before the Battle of the Pelennor Fields, Elfdag and Radwine stole away from their families in the Rohir camp at Dunharrow in Kingstead and dared each other to go on up to the Dark Door. While Radwine did not pass the door, Elfdag quietly entered, prying after the secrets of the Dwimorberg, but eventually finding himself lost in the Paths of the Dead.