The primordial sword.

"Wait, I have... I have a thing to give you..." Yuer stopped him when he was about to teleport to his castle. She took the ring that was in her space bag and continued. "Have it, it's the ring that was in the strange room with the rusty sword you have in possession."

"Hm? So you decided to show it to me?" Questioned Alvine.

"W-what? Did you know that I had taken this ring?! So why didn't you ask me to return it to you? According to you, these artifacts that look useless may be treasures! So why didn't you ask me to return it to you?" She exclaimed with disbelief. After all, this treasure is not supposed to belong to him. If they were able to reach this room it was only thanks to Alvine.