You’ll receive a chest, money, experience, glory points, union points and Ice Medals for winning a fight. The size of the reward depends on your input to the fight and how you place.
Try to win before the timer runs out or else the game will end in a draw, and there’ll be no winner. If you don’t manage to win in time, don’t despair: you still get a consolation prize for all the damage you dealt.
Also, glory points define your place in the rankings.