Guild League Cheer has been added with the 4.0 Force update.
You can participate Guild League Cheer through
All server event > Major League.
You can only participate in the Guild League Cheer for the Guilds in the Major League.
You can click the cheer button and select the Guild to confirm.
Guild League Cheer consumes 10,000 bound Zen.
When the Guild that you have sent a cheer wins, you receive the 1,000 League Cheer Points.
League Cheer Points can be exchanged with rare items in the League Cheer Shop.
League Cheer Shop