Koresh was the leader of a criminal band of mercenaries operating in a desert.
Koresh was a tan, dark-haired and dark-bearded man with a prominent nose. He wore black clothing, and a black turban.
Along with his mercenary band, Koresh was willing to trade or steal anything to increase his personal wealth. His ferocity was such that none of his many enemies dared oppose him openly.
The artwork for Koresh on the AD&D Trading Card #558 (1991) is taken from the cover of the novel The Parched Sea, which is set in the Anauroch desert, suggesting Koresh is a Bedine. However, Koresh is not a named character in that novel, and artwork is regularly reused, so it is difficult to say for sure.