The Sect-Returning Sword Casket was a magic treasure of the Mount Shu Sword Sect that was only inferior to the Saintly Celestial Sword. It was never used easily and was one of the items used to construct the Immortal Heaven Universal Sword Formation. The rule of the Mount Shu Sword Sect was that once the Sect-Returning Sword Casket was used, the Saintly Celestial Sword had to hold the fort in Mount Shu.
This magic treasure had no offensive abilities. The only use that it had was that it could capture all swords in the world. Beside the Saintly Celestial Sword, any type of sword treasure or swordplay attacks could be captured by the Sect-Returning Sword Casket. They had no room to resist.
Even very few people know about it in the entire Mount Shu Sword Sect.