It's a strategic system that introduces an element of surprise into the gameplay experience. After dispatching a monster, there's a possibility of a mysterious box materializing nearby. Upon approaching and activating the box, it unleashes a fresh horde of monsters, challenging the player to confront new foes.
It will spawn up to 8 monsters near from you.
It depends on the area around you.
Maybe it won't spawn any because no free area around you.
It will stay for 60 seconds.