Roar?
Arriving in front of the frontier city, the mountain sized demon beast didn't immediately attack, but instead curiously inspected the guardian formation. Not showing any hint of killing intent during the process. Making it seem like the earlier death of the old ancestor from the noble family had just been an accident.
"This… What is it planning to do?"
"I-I heard demon beasts in the Celestial Immortal Realm are far more intelligent than normal demon beasts… Maybe… Maybe it's trying to think of a way to undo the formation…"
"Impossible! According to the ancestor who created the formation, it's impossible for a Celestial Immortal Realm demon beast to solve the formation without trying to break it!"