At the beginning of each game, a boss will be randomly selected by the system. If the game is still undecided after 120 seconds, the boss will appear on both sides of the field, and other mice on the field will be cleared. The health of the boss is the sum of the health of all mice currently on the field of the player. During this period, the pawns will not appear according to the original rules. Each Boss has different skills, which brings more powerful threats to players.