Masters of the Universe The Board Game Assault on Castle Grayskull GameDescriptionSpecificationsShipping Assault on Castle Grayskulls new game mode puts players into one of two teams: the aggressors, who are attempting to take down the castle walls to gain control of Castle Grayskull, and the defenders, who must attempt to withstand the siege and protect its magical secrets. This expansion brings powerful tools for both defenders and aggressors alike. As the game progresses, you will choose powerful Upgrades that aid you