There was even a sky barrier protecting the Imperial Palace from the outside world. Unlike the fortress on the ground that could be seen with the naked eye, the sky barrier was invisible, but no one would question how strong the barrier was.
The purpose of having a sky barrier encircling the Imperial Palace was to protect the dragons living in the palace from intruders. Even if the dragons were strong, a sneak attack from outside the barrier was not something they wanted to get, and that was why some powerful dragons had deliberately put up a barrier following the Emperor's orders.
Xia Qiao knew about it because the celestial barrier had existed in the Imperial Palace since the days when her father was still the Emperor of Si Long, and that was why she was quite nervous when Lan Zihao was about to fly through the barrier.
