In a season, your League is determined by your Rating and Collection Power. You will advance to the next League basis the minimum rating and Collection Power of that League. You are given a choice to advance to the higher League or stay in the same League. If you choose to advance, you will receive the rewards of the higher League. On the other hand, you can also choose to stay in the same League to compete for the Leaderboard rewards. 

For example, some Ashwarohi players may choose to stay back and compete for a Leaderboard ranking, even though they have gained enough points to advance to Gajarohi. In this case, they will not receive Gajarohi rewards but if they can beat the top players in the Ashwarohi League, they will win additional BelPatr. Know more about the Leaderboard rewards here.