Edgar Heardredessunu is a merchant who can be found on the island of Orkneyjar. Just like the merchant Lutrin mac Draususa, he will arrive when some progress is made in the storyline of the faction is from. Since he is a Northumbrian, he will will probably appear when at least Ghosts of the Empire is finished, since he claims you have good relations Eanbald, but this isn't confirmed yet. He is at least when The Battle of Yngilwood has been finished.
He will, however, depart when you side against Northumbria during the quest Fort of the Thicket.
With loved reputation, he is trading the following goods at generous rates, which will change to charitable with idolized reputation: