What great deed did Siegfried do?

Siegfried, a legendary hero from Germanic mythology and the Nibelungenlied, is best known for slaying the dragon Fafnir. This great deed not only showcased his strength and bravery but also earned him the dragon's treasure and the magical cloak of invisibility. Additionally, his victory over Fafnir solidified his status as a formidable warrior and a central figure in the epic tales of heroism and tragedy.