Cross castle building upgrades grant the player the option of upgrading buildings in several castles simultaneously, regardless of the specific building’s current level. All he has to do to take advantage of this feature is select the appropriate castles and hit the upgrade building button.

Castle Selection
Castles that have enough resources and subjects and have not yet reached the building’s maximum level can be selected with a simple tap on their cell. Castles that do not fulfill the requirements are faded out and can not be selected.

Speed up/complete building upgrades
All currently running building upgrades can be sped up or completed instantly. It should be noted that all upgrades for any type of building will be sped up or completed.

Expanding the building queue
The player can expand the building queue across all castles for a few gold coins, should the building queue in some castles already have been filled.