You get multiple wooden boxes of high-end loot (some of it crap, some of it equal to Barbed Kit/Valorite Hammer in quality, if you're lucky).
A few of the "wood box/strongbox" quests are repeatable; specifically, "The Ancient World" (the minotaur quest chain) and the Bedlam entry quest chain. a lot of decent loot (and a decent chunk of my items waiting for imbuing) come from those.