In the A Song of Ice and Fire novels, Halder is sixteen years old when he joins the Watch. Jon thinks him incredibly strong, but easy to anticipate in fighting because he is short of patience, with no taste for defense.
Halder had been an apprentice stonemason before coming to the Wall and, like Grenn and Pyp, becomes friends with Jon. He helps to carve the wolf's head for the new pommel of Longclaw. He is among those who stop Jon from abandoning the Night's Watch.
In the fifth novel, Jon assigns Halder to serve at the Shadow Tower.