A union is a group of players who have banded together for mutual aid and communication. Allies can send each other lives and engage in cooperative in-game activities. You can either form your own union or join one that already exists if you reach a particular level. There are two sorts of unions: open and closed. Open unions are open to anybody, whereas closed unions require the leader's agreement to join. The union can have up to 30 players in total. Click the button in the bottom left corner of the screen to open the union's window.