As stated by Oromis, Hefring was the name of the thief who stole Saphira's egg in an effort to retrieve the three dragon eggs from Galbatorix. Although Hefring successfully retrieved one of the three eggs, he fled rather than attempting to retrieve the other two eggs. After his escape from Urû'baen, Hefring inexplicably absconded with the egg instead of turning the egg over to Brom and pursued by agents of both the Varden and the Broddring Empire, fled north. Brom's unsuccessful pursuit of Hefring took seven months and ended when Morzan found Hefring and recovered the egg before Brom. According to Paolini's page Morzan killed Hefring for the theft.
It was claimed by the Eldunarí in the Vault of Souls that they had manipulated Hefring to ensure the success of his theft. Unfortunately, they went too far and their mental nudging was finally noticed, frightning Hefring, causing him to flee.