So after the ascension of Darius I to the Achaemenid throne, he faced a plethora of rebellions from across the empire. Rebellions sprung up in Elam, Babylon, Sagartia, and Margiana, in addition to Vahyazdata pretending to be the murdered Bardiya. Babylonia actually revolted twice in this period, and Elam (Susiana) 3 times. The rebellions were not exactly completely simultaneous however and Darius, despite not having the largest of armies at his disposal, managed to deal with them one by one.
The challenge here is to have these rebellions lead to the collapse of the Achaemenid Persian empire. How can this be done and what would its implications be?