Why not put Gurhal as the ancient civilization in Algol???? The Illuminus win, only humans survive, the Ancient civilization is known then as Gods, in fact what you talk in PSIV Rykros could be an intelligent stateria with some fire lol then some hero called Landale unifies the system and becomes king, his loyal servant Lashiec is possessed by the ancient demon Falz and the saga begins xD

But the truth is that while PSO had some clues to think it was related to Algol, PSU is just plagiarism made by Sonic Team to Overworks, they have used names (planets and characters) and situations that already existed in previous games because their creative talent nowadays fails to make an original game