Which aspect of an epic is present in Beowulf? 1)Plot is complicated by supernatural beings or events; 2)Beowulf perfroms superhuman deed; 3)Beowulf performs action that affect Danes' fate.
"Then he saw, hanging on the wall, a heavy
Sword, hammered by giants, strong
And blessed with their magic, the best of all weapons,
But so massive that no ordinary man could lift
Its carved and decorated length. He drew it
From its scabbard, broke the chain on its hilt"
My thought is that Beowulf performs a superhuman deed is the aspect of an epic that is present because the characteristics of an epic are
-The hero is a legendary figure who performs deeds requiring incredible courage and strength.
-The hero embodies character traits that reflect lofty ideals.
The poet uses formal diction and a serious tone.
The poem reflects timeless values and universal themes.
Beowulf is an epic Anglo-Saxon tale. You are correct in stating that these texts contain certain characteristics which make them epics (appearance of the supernatural, superhuman deeds, and actions which benefit those around them (in this case the Danes)).
As for the quote in question, when trying to decide which aspec of the epic it speaks to, one must consider exactly what the quote speaks to. In this case, the quote is simply describing the sword which Beowulf will use to defeat Grendel's mother. His own sword, Hrunting, given to him by Unferth, will not work against the monster.
The new sword, a sword of the giants, is one which possesses supernatural powers. It is the only weapon which will allow Beowulf to defeat his adversary, Grendel's mother.
Therefore, the fact that the sword, itself, was made by giants (supernatural beings) the specific aspect of the epic to which the quote refers to is the plot is complicated by supernatural beings or events. This can be supported in two ways. First, the sword itself is supernatural. Second, it takes a supernatural object to defeat this specific supernatural being.