Buildings are special grey cards. You can't build a village using only grey cards, but you can add these cards to any other village as long as certain requirements are met.
In order to add buildings to a village, that village needs to contain support for it, like a Builder provides. A single Builder can support any number of buildings. If the Builder is destroyed or kidnapped, the buildings remain in the village but no more can be added.
Buildings have a variety of uses, such as adding power bonuses or adding options to your action phase.
List of Buildings
All items (11)