Campaign Creations

So in book 5 in the mission where hikaru has to fight through the temple of Keela there is a achievemens that says find all items in the mirror puzzle and I can't get more than 1

That obscure island up there cannot be reached (at least not with peasants) and is not one of the potential expansion sites. I think the third potential expansion site is your ally's base. If you can clear enough trees and other stuff to get a town hall close enough to the gold mine, the achievement might mark as completed.

It should work with any building other than a farm or a tower, actually. I was using a Barracks and Lumber Mill for testing purposes.