When Roy came out of Kha-Beleth's treasury, Julia happened to return with Kha-Beleth's demon sword.
Because the human form of Kha-Beleth was tall, his demon sword was naturally gigantic. It was a fiery red longsword. Standing upright, it could reach Roy's chin, which was about 2.3 meters. The edges on both sides of the blade were full of sharp serrations, brimming with the usual savage style of demons. Since its owner had been a flame demon, this demon sword naturally burned with raging flames. As a demon lord's sword, it was also extremely powerful.
Overall, the style of this sword was not suitable for Julia, but Roy could not just abandon such a powerful weapon so easily, so he planned to modify it.
Most importantly, this sword also contained one of Kha-Beleth's soul fragments, and it would reject anyone other than Kha-Beleth from using it, so it was unusable without modification.