Shinsoo initially served Aria, the Empress before Cygnus, until Aria was killed by the Black Mage Commander Lotus. Shinsoo entrusted the Skaia, a legendary jewel said to glow in the hands of the Empress, to Phantom, who kept it safe for a hundred years before returning it to its rightful owner. However, before Phantom returns it, the Black Mage Commander Hilla attempts to pass off as an Empress with a fake Skaia; the Knights cannot confirm if it was real as Shinsoo was not present for an unknown reason.
Much later, Damien kills Shinsoo, who is shortly resurrected by Cygnus after awakening her powers. After that, Shinsoo leaves Ereve. In the Cygnus Knight Quest Shinsoo's Call it is revealed that she left for the purpose of protecting Cygnus, who is on the way to becoming the fourth Transcendent.