Giedi Prime has no place for the weak. Feyd knew it the moment he set foot on it and couldn't see colors under the black sun. On Giedi Prime everything was black and white. Simple as that. It was a planet with few rules and a community, which simply did not cared to be controlled by the Known Universe. But Feyd knew the rules. He knew how to play by them.
But sadly, his uncle knew too. The Baron. A man, who seemed like he has all the power Feyd could only wish for. His brother, Rabban was unfit to rule and their uncle recognised that.
When they've got the news that the Atreides heir became the leader of the fremens on a planet, what Feyd always dreamed about, it ironically worked in his favor. He was named na-Baron, heir of House Harkonnen and Arrakis bacame his to inherit. But Arrakis wasn't his only gift.