Foible fragment

The Foible fragment, also called Empereor Belos' fragment is one of three magical fragments of the ancient Calamity Sword currently in possession by Emperor Belos of the Boiling Isles. It's the only fragment that Samuel Colt does not possess and the only thing from completely restoring the Calamity Sword.

Background
Three years before Luz entered the Demon Realm, the Foible fragment was sent to the Boiling Isles after the sword's destruction, detected and retrieved by Emperor Belos himself, who sensed its power to be similar to the power of the titan's blood. Belos has studied the fragment of the upper blade and was only able to locate scraps pertaining to the Calamity Sword, along with another object simply called the Calamity Box.

The fragment is kept secured inside his palace, where Luz made note of it, citing that she saw an strange runic symbol on it before moving forward throughout the palace.