Who made the sword Beowulf used to cut off Grendels head?

After a long time, Beowulf reaches the bottom of the lake, where Grendel's mother waits for him. She reaches for him, but his armor protects him. He tries to cut her, but his sword can't cut her. The two begin to wrestle, but neither gains the upper hand in this combat. Beowulf spies a large sword nearby, it is an enormous weapon forged for giants. He manages to grab it, and in one mighty blow, he beheads Grendel's mother. Light enters the murky water then. Beowulf is still angry, however, so he also beheads Grendel, who lies dead in the cave.