Gram

Gram is the strongest Demon Sword also known as the Sword of the Sun and the Demonic Emperor Sword.

Summary
The strongest Demon Sword created, Gram was previously wielded by the original Siegfried who used it to slay the Dragon King Fafnir, though Fafnir was later revived by the Norse Gods.

In the present days, it was wielded by Siegfried, the descendant of the Original Siegfried, prior to his death in which Gram abandoned Siegfried and chose Yuuto Kiba as its new wielder.

Abilities
Gram is a Demon Sword with Dragon Slayer ability imbued. It also has the destructive power equivalent to that of the Durandal, which causes Yuuto to compare it to a combination of Ascalon and Durandal, but does not need to be charged to do destructive attacks. It is also sharper than the Holy Demonic Sword he creates.