For the shield, head to Aleroth, keep going to the ministry at the far end and use the teleporter to get inside the building.
The entrance to the Hall of Echoes should be marked on your map. It is far below the talking tree that asked you some riddles, a little south of Keara's flying fortress entrance, east of the Red Hammer Tribe teleporter shrine. Look for the beach there with a few dragon skeletons further inland; the entrance is at the back.