The spiritual item held the same name as the magical sword used in the legend of Beowulf. Apparently, the sword became tougher and sharper from the blood of slain enemies that blocked ones path, but Knight Leader had most likely had Telesma act as the blood so that the a large amount could be compressed into it in order to give it a tremendous amount of destructive power.

Toaru Majutsu no Index vol.18 ch.5 pt.3