Rank in the top places (4 to 2, depending on the requirements of the league) at the end of the round to be promoted to the next league. Your position in the league depends on the rating.
Also,  if you complete your league's rating requirements, you will instantly go to the next league.
Players who could not take top places either move to the previous league or stay in the same league. It is impossible to drop below the Wooden League and the Orbeuseus League.
From the Orbeuseus league, you can only move to the next league after the timer has expired; the instant transition becomes unavailable.