With the barrier activated, the Dry City would have only four entry points, precisely the points already controlled by the local army on the wall.
At these points, only those who obtained the soldiers' authorization at the entry posts could reach the city protected by this entire dome. If this were not achieved by one of the visitors, it would be impossible for one of them to reach the territory of the Dry City unless, of course, that person destroyed the barrier!
And with that, situations like the arrival of Elen and Elena, which had happened earlier, would no longer be possible. After all, the dome-shaped defensive barrier would stop all living beings who tried to enter this region from the sky.
In fact, aside from living beings and spiritual attacks, anything else could enter this protected area. An example of this was the gases and the spiritual energy itself, which could pass through these dome areas as if there were no impending action.