Surtr

Surtr is foretold as being a major figure during the events of Ragnarök; carrying his bright, flaming sword, he will go to battle against the Æsir and Vanir with his kin. His ultimate fate is to kill the Vanir God Freyja, Goddess of Love. Afterward, the flames that he brings forth will engulf the Earth.
Until the apocalypse comes, he guards the entrance to Muspelheim with his sword to keep out anyone who would try to enter.
Surtr forged a legendary fiery sword which he used to destroy Asgard. This sword is one of the strongest weapons among all the Realms, rivaling or possibly exceeding weapons such as Mjölnir and Gungnir.