Mithridates VI of Pontus (135–63 BC)
Claiming descent from Darius I and Alexander the Great among others, and well known for his mastery of poisons and their antidotes, Mithridates VI of Pontus was one of the greatest enemies of the late Roman Republic. He was born in the Asia Minor kingdom of Pontus. When he was in his teens, his father, Mithridates V, was assassinated and his mother (who most likely had a hand in the plot) took up the regency. Fearing for his life (his mother preferred his docile younger brother), Mithridates and several close friends fled the capitol, making allies among his father's commanders and the border regions. After several years, Mithridates returned, poisoned his mother and brother, and became de facto ruler, taking his sister Laodice as the first of several wifes he would have in his lifetime.
After his mother, Mithridates trusted no one in his family. He kept his younger sisters under virtual house arrest to prevent them from siring potential rivals to his power. After Laodice gave birth to a son that was clearly not her brother-husband's, he poisoned her. Several of Mithridates' wifes and their children met similar gruesome fates. When his nephew Ariarathes VII of Cappadocia rebelled against being a puppet of his uncle, Mithridates personally killed his nephew and installed the son that was not his as the new king. Eventually, the power plays among the kingdoms of Asia Minor caught the attention of the Roman Republic, as several of said kingdoms were client states of Rome. Mithridates attempted to overthrow Nicomedes IV of Bithynia, but this failed, and Rome sent two legions to assist Nicomedes in retaliation. Their attack failed, and Mitrhidates went on the offensive, starting the First Mithridatic War.
Mithridates seemed to have endless armies at his disposal. Many of the cities of Anatolia sided with him, and he drew support from barbarians all around the Black Sea region. In addition, Tigranes the Great, King of Armenia, was his son in law, and waged his own campaigns against the Romans in Syria. In 88 BC Mithridates orchestrated a wide spread slaughter of Romans in Asia Minor, an episode called the Asiatic Vespers. Alarmed by both this and the siding of Athens and other Greek city states with Pontus, the Republic sent Sulla and several legions to defeat Mithridates. Sulla defeated Mithridates' top general Archelaus at the battle of Chaeronea, but not before besieging Athens, which ended in a sack of the once great city.
Sulla was in a precarious position: his enemies had taken over the Senate and had sent rival legions to finish the job. He and Mithridates were both in dire need of peace, and a treaty was hastily written up. In it, Mithridates promised to evacuate all the regions he had conquered, and Rome promised not to invade Pontus itself. While Sulla went back to Rome to slaughter his enemies there, Mithridates dealt with the other legions, called the Fimbrians. They foolishly attacked Pontus, were defeated, and Pontus for the moment was left alone. This was called the Second Mithridatic War. The third war was started when Rome attempted to annex Bithynia after Nicomedes died and left it to Rome in his will. Calling the will a forgery, and declaring Bithynia his by birthright, Mithridates drew up another huge army and attacked Rome once again, defeating Sulla's subordinate Lucullus, who had also failed to invade Armenia, Mithridates' key ally.
Gnaeus Pompeius Magnus, who had recently defeated Quintus Sertorius and Spartacus, was the next person called up to defeat Mithridates. Pompey defeated Mithridates in Pontus in 66 BC, but the king fled to first Armenia (which Pompey would also subdue), then the Caucasian mountains, where he reached the Bosporus. His son Machares had been ruling Bosporus for some time, and had cast his lot with Rome. After killing Machares, Mithridates further plotted to attack Rome once more. But another son, Pharnaces, led a revolt against his father. Trapped in a citadel with no means of escape, Mithridates and several other family members took poison. Ironically, Mithridates' experiments with poison and antidotes meant that the poison failed to kill him, and he had to ask a Gallic bodyguard to kill him with a sword.
Mithridates' secret master antidote, the Mithridate, would be sought after by emperors and kings long after his death.