Finally, Allen most likely came to the area where he will face the Boss monster. If you are wondering how he said that then it was because suddenly after coming to that place he began to feel exactly the same feeling when any Boss monster appeared inside of the dungeon. Suddenly everything becomes silent and at the time even after advancing in that place he did not find any monster.
He already suspected that most likely this was the territory of the Boss monster and until the Boss monster did not give them the order those other monsters would also not act in that place. Because of this even roaming around that place for sometime he did not face any Monster and also the surrounding place became silent.