Lines 800-900

(801-810) When the thanes try to attack Grendel, their blades fail to damage him. Grendel had taken away the harm caused to him by any human weapon, but his passing from the world would be painful still.

Sigemund slaying Grendel

(811-820) Grendel's powers fail him. Beowulf holds him in a handgrip, and Grendel can not escape. A wound appears on his shoulder as his arm is broken off. Beowulf wins, and Grendel flees to the fens, fatally wounded.
(821-830) He is expected to die soon, and the hopes of the Danes are fulfilled. Beowulf had saved and protected the hall, and he is happy with the the fight and the courage he had shown. He had boldly fulfilled his promises; ridding them of distress and humiliations.
(831-840) They can see proof of this by the display of Grendel's hand high up in the roof. Beowulf has put up Grendel's entire shoulder and arm, and all can see the power in it. Morning comes and and many warriors gather at the hall. Different clan chiefs from far away came and wonder at the footprints left by Grendel.
(841-850) Grendel's death is regretted by no one who sees the tracks. They can see the marks left when he fled, bloodying the path and taking himself to the mere. The bloody water surges as Grendel thrashes, drowning himself at the bottom of the swamp. He dies there.
(851-860) Then the retainers and noblemen all ride away in high spirits. Beowulf's doings are praised over and over again. They say that no one on earth is better to rule a kingdom than him.
(861-870) However, they do not put any blame on Hrothgar; he was a good king. Sometimes these retainers break into a gallop, letting their horses race wherever there was a good stretch of road. During this time, a thane of the king's household, a traditional singer who was educated in the tales of the past, revises an old song and sings the tales of Beowulf.
(871-880) The man recites with skill, retelling Beowulf's triumph in well made verses. He tells about a legendary warrior named Sigemund, who achieved many feats and marvels. He tells of his struggles, wanderings, feuds, foul doings, and things unknown to many.
(881-890) The man tells how Sigemund and his uncle Fitela were always partners in fights and friends in need. They killed giants with their conquering swords. He goes on to tell about how Sigemund's glory when he had killed a dragon guarding his treasure, and how he had dared to go alone and without Fitela.
(891-900) Sigemund's sword pierced the dragon's scales, killing the dragon. He obtained possesion of the treasure, and loaded a boat with it. The hot dragon then melted. Sigemund's name was known everywhere; he was brave and adventurous and protected his warriors.