You can check all methods with the MineChessAPI class.
Events
// Event called when the arena starts.
@EventHandler
public void arenaStarts(ArenaStartEvent event){
Arena arena = event.getArena();
}
// Event called when the arena ends.
@EventHandler
public void arenaStarts(ArenaEndEvent event){
Arena arena = event.getArena();
GamePlayer winner = event.getWinner(); // null if tie
GamePlayer loser = event.getLoser(); // null if tie
GameEndsReason endReason = arena.getEndReason();
}