An Alliance is a group of Nations that have banded together to face a serious threat. The nations of the Alliance will combine their forces to destroy whatever they face. Alliances depend on nations' feelings toward each other. Friendly nations are far more likely to work together than nations that dislike each other, or that hold radically different social and moral ideals. One of the player's major tasks is keeping tension between nations as high as possible to prevent them from grouping up.
It is possible for an Alliance to form that targets something other than the player. If a Rival Old One is perceived to be more dangerous than the player, the Alliance might focus on it instead. If the enemy is truly deadly, it is even possible for the player to enter the Alliance and help the nations for a time. Alternatively, the player can set up comparatively minor threats for an Alliance to attack, giving the player some room to accomplish their own goals. For example, the player could rile up the Orc tribes with the Hordemaster and try to convince the Alliance that the orcs are the main enemy to be contended with.