Reference article
Egg Island Tournament
Egg Island Tournament is one of Adventure’s three major tournaments.
Entering and progressing
Win its racing and battling branches, then defeat the Mayor in both a race and a battle.
Tournament structure
Finish the race and battle branches to unlock the champion challenge. The champion must be beaten in both disciplines. Leaving a branch halfway through requires restarting that branch, as explained by the tournament introduction.
Champion
The champion is 
Mayor. Train and choose equipment for both races and battles.
