Soul Eater: O que é o excalibur?

Almost nothing certain is known of Excalibur's history. However, it is evident that Excalibur's birth/creation pre-dates that of the Demon Weapons, as Excalibur is mentioned as having served as the inspiration for their design. His exact species and origins are a complete mystery, though they may hold some degree of divine creation.
During the Grim Times, Excalibur may have served directly under Shinigami as one of his Eight Powerful Warriors alongside the other Great Old Ones, where he partook in various confrontations as part of a long lasting battle against the Witches. However, at some point after the events surrounding the devolution of Asura into the first Kishin, Excalibur decided to retire to his perennial residence within the Eternal Cave, located in the northern part of the British Isles, where he has remained ever since.

Over the course of the centuries that were to follow, Excalibur's abode has been frequented by numerous prospective candidates, all of whom had undertaken the expedition with the singular intention of claiming the legendary sword as their own. However, due to Excalibur's diverse personality defects, the majority of these potential applicants ultimately proved unsuccessful in wielding the sword for a prolonged period of time. Counted amongst this unfortunate number are the likes of both Franken Stein and Sid Barett.