Arcturus Mengsk is a Terran of the Koprulu Sector who founded the Sons of Korhal and the Terran Dominion.

From the Great and Brood Wars to the middle of the second Great war, he ruled the Dominion building up its military might while at the same time commissioning several clandestine operations involving mysterious benefactors. Arcturus had also spent a large amount of Credits to pursue a rebel group that splintered off the Sons of Korhal officially known as Raynor's Raiders specifically their founder and leader Jim Raynor.

For more information see Arcturus Mengsk on the parent site