Cover of Darkness
The cover of darkness is special building of necropolis town. It creates an unexplored area of 20 square radius around the town for opposing players, which is regenerated at the beginning of the owner's turn. The effect is similar to the cover of darkness (a sphinx on a platform emitting a shroud) found on the adventure map. A Tower town with a lookout tower can (partially) cancel the effect for tower's owner. However, a skyship does not cancel the effect.