You must have your Dragonform, otherwise you can't remove the shield, because of humans can't fly in the sky to reach the place
I go explore and swim to 2 other places and kill all enemies in the Orobas Fjords I can, in humanform only.
But the enemies are at L22 I think, so be careful!
Make sure you explore ALL area in Brocken Valley, because there is more to discover than at first sight seems! Good luck!