Arcturus Mengsk is a prominant antagonist in the StarCraft real-time strategy PC game series by Blizzard. He is a Terran born on the planet Korhal IV who lead a rebel faction known as The Sons of Korhal with his fellow Korhalians against the oppressive Confederacy of Man who dominated the Korpulu sector. He ultimately succeeded using genocidal tactics and treason and was responsible abandoning former Confederate assassin Sarah Kerrigan, on Tarsonis, which resulted in her transformation into the Queen of Blades.
Disgusted by this, fellow rebel Jim Raynor cut ties with Mengsk and established his own group of rebels entitled Raynor's Raiders.
Upon the fall of The Confederacy, Mengsk established The Terran Dominion, where he crowned himself Emperor. However, he was not much different from the people he sought to replace and continued to rule via manipulation and terror. Raynor's Raiders constantly have tussles on with the Dominion on many worlds in their quest to overthrow Mengsk.
He had a son named Valerian Mengsk, who eventually led Dominion forces along with Raynor on a full-scale assault on planet Char in order to de-infest Kerrigan.
In 2506, he finally met his demise at the hands of a vengeance-thirsty Kerrigan on his home world of Korhal.