 Complete the following phrase:  The assassination of Alexander Severus 222235, the last of the Severans, brought to an end the Augustan Principate, and the empire descended into its third crisis, this time lasting nearly fifty years. Twenty five emperors obtained power in the space of forty-nine years, with at least fifty one claiming it. Most were either murdered or died in military campaigns against Romes enemies that were now pressing hard on her frontiers. In addition to instability in goverce and civil war the crisis years were marked by hyperinflation, 