Originally Posted by
Enosh
iirc in the first chapter they mention that the probe has the same tech as the unknown force that raided some republic and empire planets, so
Valkorion has his sons raid the republic and empire -> they win but Arcann gets injured on the sith planet -> they come back present their victory and Arcann kills his brother -> the events of the first chapter happen -> outlander gets frozen and Arcann launches his full scale attack on the republic and Empire
I guess it's kinda stupid since the sith planet looks a lot like Korriban but iirc Marr only mentions them attack some outposts