After speaking to his younger sister, finding the last two holy sword cards became the top priority for Rhode. Meanwhile, he also learned from his younger sister the holy sword cards existed not only because of their power, but because of their 'attributes'. The truth was that after the Order Star was destroyed, his younger sister came up with ways to recreate a device that could truly resist and convert Chaos.
That was when Cassidy was created. However, without the need for his younger sister to mention it, Rhode knew that her experiments failed because Cassidy's power was 'contrast'. In that case, no matter how much Chaos she converted to Order, she would also create an equal amount of Chaos at the same time. Besides, there was only one Cassidy, and there were times when she couldn't hold on.