I once did the final boss of grizzlehiem and got these items .Silverback wildclaw .coat of the elixer( best grizzleheim life robe) .evenhanded robe( best grizzleheim balance robe) .coat of the naiad( best grizzleheim storm robe) Since they were all useless though i sold them for 1200 gold each and they are no auction. I kept the wildclaw though.
You have to be at least Level 40 to get the quest to defeat Jotun. His brothers are optional, and if you defeat them first, they will not be in the final battle against Jotun, making that battle slightly easier.