Morgause was the Goa'uld Queen of the System Lord Manannan mac Lir.
Biography
Background information
She was gifted to him upon his ascension to the rank of System Lord, which he attained by defeating the System Lord Balor. Manannan sent Morgause to quell a rebellion in his holdings on Earth by killing the rebellion's leader, a Tau'ri named Arthur. In order to kill two birds with one stone, he also commanded her to mate with Arthur, in order to enhance her ability to produce blendable offspring. Somehow, Morgause's host became pregnant, and before she could kill Arthur she went back to Manannan. She gave birth to the human, a boy who was later implanted with one of her own larvae, Mordred, who would go on to become Manannan's greatest underlord and slay the human Arthur. Recently, Morgause has become barren. (RPG: "Living Gods: Stargate System Lords")