Very little information is given on Durak. Most likely he was either an avatara of the Nine or a minor avatara of the Nine in training. Whatever the case, Durak would most likely be an avatara by the time of Soulblighter's war.
It is considered speculation that he was a druid or avatara of the wild. But given the etymology, history, and the lore of his name--Durak should definitely be considered a Druid avatara of the wild, and living in Forest Heart is the highest probable outcome given that the journal made no entry about him in Soulblighter's war. Some have hinted that he was the apprentice or son of Cu Roi.
It is unknown if Alric tried to set up a replacement of the Nine, but if so, Durak would have been a likely candidate but may or may not have rejected the offer, preferring to stay in Forest Heart (or in the wild). But if accepted he probably tried to hold off the forces of darkness with the Forest Giants in Forest Heart. Unfortunately, this seems to be met with little success given the results of the mission "The Relic."
It is hypothesized that Durak could take the form of a giant Were-Bear or Were-Wolf. He could also launch blasts of green energy and summon giant roots from the ground. Durak also had an ability where he could transform himself into a Forest Giant and summon roots while in this form--others have also stated that he can take the form of a green griffon and has a home in a very large tree which he uses to regenerate his power and health. Durak also used hawks for scouting.