An alliance is a group of cities under a commander. The greater the number of cities, the more the alliance can do for its members.
The game allows an alliance of the right size to establish a site, a nest, within which members receive the joint benefits that the alliance has obtained. Starting at a total of 15 members, the site can grow as the number of members grows. The game allows an alliance center, up to four outposts and a resource building, all constructed using stone donated by the members.
The alliance tab at the bottom of the screen is the link to information about the alliance, and to the various alliance activities and benefits.