"What am I missing here?" William couldn't help but wonder. Something kept bothering him. He missed a little thing, and he didn't have time to consider what it was right now.
Even if he knew the monster tide's true and scary nature from the start, he related everything to the techniques he gave to Berry.
If so then the monster leaders would bring the three gates here, to fasten their invasion of the clan and find him or Berry or both.
However, from such a layout, it only meant that the monster army leaders didn't only want to kill him and Berry, but they wanted to destroy and totally annihilate this entire clan.
And that would be explained by how the monster leaders arranged the other two gates to isolate the clan, buying themselves enough time to do anything they wanted with the clan without any outside interruption.