When the Allied forces saw the undead creatures, their expressions changed. They didn't expect Zhao Hai to be a ghost cultivator and to be able to command so many ghosts.
Skeletons, zombies, malicious ghosts, and evil spirits were collectively called ghosts in the world of cultivation. All cultivators who cultivated ghosts were either called ghost cultivators or the devil race. However, strictly speaking, it was more accurate to call them ghost cultivators, because devil cultivators were sometimes those cultivators who specialized in cultivating the devil sect's techniques, not those who cultivated ghosts.
As a result, when the Allied forces saw Zhao Hai release the skeletons, they immediately thought that he was a ghost cultivator, and an extremely powerful one at that.
