Oreioth had always been cruel, but after his self-exile to Red Larch with only the company of his undead servitors, he became a true megalomaniac. He barely recognized his own name and dreamed of founding a kingdom of undead minions with himself on the throne.
Oreioth was born into a noble family in Baldur's Gate. In his youth, he showed a cruel streak that embarrassed his family, so they hired a tutor to channel his undeniable intelligence and curiosity into more positive outlets. Unfortunately, Oreioth's tutor was secretly a necromancer in search of an apprentice. Oreioth quickly became that apprentice and did all manner of dirty jobs for his master. When his usefulness ended, the master necromancer sent Oreioth off to make his own way in the world.
He traveled from town to town, finally establishing a lair near Red Larch. There he began his necromantic research and plotted dreams of conquest. However, in 1491 DR, some adventurers found his cave and they defeated Oreioth and his undead minions.