You should be able to transform into a human and take a teleporter north of that anti-dragon shield to get to the area with the lever to disable it. Is that where you are getting the cutscene of the shield?
From the D2:ED
walkthrough, Broken Valley flying fortress section:
-To disable the anti-dragon zone around the mine, you'll need to find a
generator just west of the mine and flip a nearby lever in human form.
-Another lever can be found just southeast of Lord Lovis' tower.
-The next zone to disable requires you to land in the area only accessible
after flipping the prior lever (west of Lord Lovis' tower, just north of the
still active zone). Find and use a teleporter after you land, then locate and
flip the lever at the top of the new area to disable all but one remaining
anti-dragon zone.
-Next, disable the barrier by landing on a platform on the west side of Maxos'
temple and flipping the lever there. Geshniz's Headquarters can be accessed
via the teleporter on this platform.
-The last anti-dragon zone can be disabled by flipping a lever not too far
west of the zone itself (like the others, it's found inside of a thick-walled
fort easily visible on the map).
Other than a few Black Ring members and random loot I don't think there is anything essential within that anti-dragon zone.
Welcome to the forum.
