Whenever you clear an area, either by defeating an Area Boss or a Zone Boss, you increase the "Areas Cleared" counter on your account. When the number of areas cleared hits specific values, you earn one of three bonuses: an increase of 1 to your spirit collection maximum, an increase of 0.5 to your maximum team cost, or an increase of 5 to your maximum number of friends. As the number of areas cleared increases, the more areas you need to clear in order to reach the next bonus.