Who is Cyrus Foss from The Game and what is their importance?

Cyrus Foss is Hayley's mortal father. He was the King of ancient Greece (he was called Sisyphus at this point) and married Merope, one of the seven sisters. In Greek mythology, Sisyphus is punished by having to push a boulder up a hill only to have it roll back down to the bottom each time he neared the peak.