Here's how it works. With the added content of organization (or guild) housing, the players can now create whole cities of their own including player shops. These cities function both as player housing but also the setting for the core content of the expansion; the aliens stage attacks on these cities, forcing players to repel the invasions and defend their cities. Very cool stuff. If an organization has one level two player and one level two hundred player online, the AI will send a few aliens which are in the level two range and in the level two hundred range, so in this sense, the expansion can be played by everyone. Also worth mentioning is the stunning new array of decor available. You can create anything from swimming pools to huge lobbies in the new houses. The look and feel of this is great and adds to the already immersive gameplay!