Every time you go offline your dungeon appears in the Attack mode and other players may find and raid it. There must be something about your dungeon that attracts other players and makes them attack you - it might be the gems in your ritual, the amount of gold you have or the fact that they have already had the same layout before and know how to pass it flawlessly. It is not against the rules to raid the same dungeon if one sees it in the Attack mode and you are not being discriminated against as a player in this case in any way.