The Hall of Echoes is the final section of D2:ED, and the subquests required to enter involve doing stuff the fjords, Broken Valley and Aleroth (which you will gain access to once you have explored enough of the fjords).
After you teleport to the fjords there are opponents along that mountain path (if you didn't clear them earlier) and a couple beaches, as well as a couple caves and a mine. A barrier blocks off access to the rest of the fjords, though, until you get into a bunker on a cliff wall to deactivate it (and the anti-dragon shields surrounding the bunker).
Don't forget to return outside on Sentinel Island, as well, since you auto returned when there were still a few opponents left. You can also now get the treasure in the boat in the tree (and either use it yourself or complete that quest), as well as find a few treasures in wyvern nests (one in particular is desirable; the rest are random), and if you get away from the island there is something else of note to find.
I don't recall there being weapons in the battle tower chest at the start (there are dragon armour pieces). I delayed taking over the battle tower, though (clearing some of the fjords before heading to Sentinel Island, and as much of the rest of the start I could do as a human before getting the battle tower), so may have just had better weapons by then.
