this eventually led to a conflict with the Roman Empire ended by the efforts of Lucius Murena.  
Two Romans, Lucius Magius and Lucius Fannius defected and offered their services to this ruler. Ariobarzanes I of Cappadocia gained much of his land by defeating this ruler while serving under the general who would defeat him. With the Bithynian prince Nicomedes, he sought to partition Paphlagonia. Cassius Dio records how Plutarch slew him, and his first wife Laodice was also his sister before he killed her. His daughter Cleopatra was given in marriage to Tigranes - this eventually led to a conflict with the Roman Empire ended by the efforts of Lucius Murena.  This man's troops were led by the Greek general Archelaus in a conflict that saw his forces lose at the Battle of Orchomenus and the naval Battle of Tenedos.  For 10 points, name this king of Pontus that instigated the Asiatic Vespers that allegedly consumed a pellet of various chemicals to develop immunities to them.
Two Romans, Lucius Magius and Lucius Fannius defected and offered their services to this ruler.
Mithridates the Great or Mithridates Eupator or Mithridates the VI Pontus