The league system is available for single, co-op, and collection events. There are the following levels: Bronze 1-3, Silver 1-3, Gold 1-3, and Emerald 1-3. Later on higher difficulty levels will be unlocked.
A league always consists of a group with 20 players or co-ops who compete against each other. This is done so that you only have to compete against 19 other players/co-ops instead of several thousands.
At the end of an event, the top players/co-ops in a group of 20 will be promoted to a higher league, while the last ones will be relegated by one league, if they are not already in the lowest one. The higher the league you play in, the better are the rewards you receive.
It is important to mention that now each of the 20 players or each co-op receives a reward. The players/co-ops who were the best ones will of course get better prizes. Therefore always try hard! :)
Finally, there are Mystery chests that you can open with the Chest keys, Tournament coins, and Victory coins you’ll win. These offer a wide range of extra rewards, from profile pictures to upgrade materials!