Complex sentence: But the last king, Nicomedes IV, was unable to maintain himself against Mithridates VI of Pontus, and, after being restored to his throne by the Roman Senate, he bequeathed his kingdom by will to the Roman republic (74 BC).
Split into simpler sentences: But the last king, Nicomedes IV, was unable to maintain himself in power against Mithridates VI of Pontus. After being restored to his throne by the Roman Senate, he bequeathed his kingdom through his will to the Roman republic (74 BC).