As to what such technology might be used for, who can say? As a weapon? There are any number of ways you could imagine for such a device to be used offensively. To acquire something they need? Or as an escape route - perhaps this world is at war, and they want to make sure they have a way out. They could be doing it to establish contact and trade with other realities.

Perhaps they are doing it simply because they can. It might be simple curiosity.