The guard is a boss from Virtual Boy Wario Land that guards the boss door of every boss stage. It is a small robot armed with both projectile and melee weapons, and attacks Wario in different ways, but its main attack is by trying to jump on him with its spiked head. After it lands, it leaves its weak spot exposed, and Wario can jump on it. Once he does this twice, the guard is defeated and Wario can access the boss.
Once a guard is defeated, it is gone forever unless the player starts a new file.
The guard is encountered four times. In all four encounters, the guard has different attacks that make it more difficult to defeat than in the previous encounter. In Hard Mode, the guards attack much faster and the speed of all their attacks is increased significantly.