Rather than let go or flee from the mead hall, Beowulf tightens his grip and refuses to allow Grendel to escape. Grendel panics and struggles with all his might to break free from Beowulf's grip. Beowulf's grip is so tight that it crushes Grendel's talons, rendering them useless. During the course of their struggle, Grendel and Beowulf destroy the inside of Herot Hall, and Beowulf's soldiers try in vain to help him. However, Grendel's magic skin protects him from their weapons, and Beowulf must finish the battle on his own.

The violent battle ends when Beowulf rips Grendel's arm from his body, and Grendel slinks off to his den to die. Beowulf fatally wounds Grendel and keeps his detached arm as a victory trophy. Following the battle, the Geat warriors and Danes celebrate Beowulf's victory, and Grendel's mother begins plotting her revenge.

The battle between Beowulf and Grendel is long, brutal, and bloody. It was always expected that the great showdown between the Geatish warrior and the hideous bloodthirsty monster would be like this. After all, there's something not of this world about Grendel, and so it would always take something a bit special to defeat him.

Enter Beowulf, the proud Geatish warrior. He doesn't flinch when Grendel attacks him and tries to devour him as he's done with countless Danish warriors in the past. When Grendel grabs Beowulf by the arm, our hero keeps his cool. Instead of trying to extricate himself from the creature's fearsome grasp, Beowulf grabs hold of Grendel, indicating to the monster in no uncertain terms that he's not dealing with just any regular warrior.

In the ensuing melee, Grendel tries to escape from Beowulf's iron grip, but Beowulf won't let him; he's got the monster right where he wants him. While Grendel tries desperately to thrash himself free, his talons are broken, which makes him much less of a danger. Even so, he's not done yet. He comes at Beowulf, attacking him as his very life depended on it. But Beowulf gives as good as he gets, and Heorot shakes as the hero and the monster throw each other all around the mead hall.

Finally, Beowulf gains the upper hand as Grendel senses his strength draining away from him. He rips off the monster's arm, and Grendel, mortally wounded, slinks off to his den to die, never to darken Heorot's door again.

When Grendel arrives at Herot, he finds the Geat warriors deep in sleep and plans on devouring each of them alive. However, Beowulf remains awake and patiently waits for the perfect opportunity to attack the ferocious monster. Grendel proceeds to rip the door open and savagely eats a sleeping Geat warrior. Grendel then attempts to devour Beowulf, who quickly grabs him by the arm and does not let go. The instant Beowulf clutches onto Grendel, the monster recognizes that he has met his match and tries to free himself. However, Beowulf tightens his grip and prevents Grendel from escaping the hall. As Grendel begins to violently thrash his body, Beowulf breaks his talons in his strong grip.

Beowulf and Grendel engage in an intense struggle as they throw each other against Herot's walls and overturn the heavy benches and tables. The entire mead hall shakes during the violent battle, and the Danes are horrified by the sound of Grendel's chilling shrieks of pain. The Geat soldiers attempt to help Beowulf during the struggle by hacking at Grendel's body, but their weapons cannot pierce the creature's skin. As the battle continues, Grendel recognizes the futility of opposing God and can feel his strength diminishing. After a prolonged, violent struggle, Beowulf ends up ripping off Grendel's arm, and the mortally wounded monster returns to his den at the bottom of the marsh. Following the bloody, intense battle, Beowulf hangs Grendel's claw, arm, and shoulder from the rafters of Herot.

The battle between Beowulf and Grendel is full of a mixture of excitement, horror, violence, and glory. To begin with there has been a lot of suspense rising in the 735 lines leading up the battle. We know that Grendel has so far been undefeated and killed a countless amount of men prior to Beowulf's arrival. Beowulf himself recognizes the danger he will encounter and does not seem particularly worried that he could die in the upcoming fight.

When Grendel arrives at the hall where Beowulf and his men are housed, he attacks immediately by mauling and devouring one of the men. He is then about to pounce on Beowulf too, but Beowulf seizes him in an arm-lock more intense than anything Grendel has ever suffered before. Grendel panics and tries to retreat at this point, but Beowulf does not let go. Locked in Beowulf's grip, Grendel starts thrashing around, causing the two of them to crash into everything in their way as they grapple with one another. Even the mead benches are being smashed. All the Danes within earshot are horrified by the pain-filled wail of Grendel as he tries to free himself. The fight apparently lasts for quite some time, and eventually Grendel feels himself losing his strength. Beowulf has not stopped clutching him the entire time. Suddenly the hide and muscles of his shoulder split apart leaving Grendel with a bloody hole where his arm had been. Only then is he able to flee back into the countryside and go home to die in his lair. Beowulf is left holding the arm as a trophy and hangs it up on display.

In the epic poem Beowulf, Beowulf engages in several battles with supernatural monsters: Grendel, Grendel's mother, and the dragon.

The battle against Grendel's mother contains an important instance of situational irony. Early in the poem Grendel's origins and ancestry are described by the poet:

They split 

Into a thousand forms of evil--spirits

And fiends, goblins, monsters, giants,

A brood forever opposing the Lord's 

Will, and again and again defeated. 

It is this reference to "giants" that is most interesting. Biblically, giants are said to have inhabited the earth in pre-history. This links the Beowulf story to Christianity and the Old Testament. But it also sets up a surprising development during the fight between Beowulf and Grendel's mother a little later in the story. 

When Beowulf attacks Grendel's mother at the bottom of the mere, he finds the sword Hrunting (a gift from former rival Unferth) useless. Without a weapon he is in grave danger, having survived so far only because of his protective mail shirt. 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.

This is the weapon that saves Beowulf's life. Grendel's mother cannot overcome it's magical power and Beowulf uses it to decapitate her. 

The irony here is that she is killed by a weapon created by her own evil ancestors. Beowulf was pretty much out of options at this point, and the unexpected appearance of a magic sword saves him at the last moment. We call this plot device "deus ex machina," which literally means "God from the machine." It refers to the last minute solutions and rescues we so often see in literature and movies. The ironic twist at the end is also still popular among modern readers and viewers. 

Beowulf informs Hrothgar that if he should die in battle, the treasure Hrothgar has given him should go to Hygelac, Beowulf's uncle. Beowulf promises the sword, Hrunting, to Unferth if he should die.

Beowulf jumps into a large lake and is gripped by Grendel's mother. She can not hurt Beowulf because of his armor. But she manages to drag him to her lair (like a battle hall) while other monsters attack him while he is in the water.

He finds himself in her home, out of the water, away from the other monsters, and near a fire. He swings his sword at Grendel's mother but it has no effect: "this was the first time for the rare treasure that its glory failed." Beowulf throws down his sword, grabs Grendel's mother by the hair, and pulls her to the ground. She reciprocates, pulling him to the ground. She is on top of him and tries to use a dagger but it does not pierce his armor.

Among the armor in the lair/hall, Beowulf sees a "victory-blessed blade, an old sword made by the giants." He manages to stand up and grabs this sword. He swings, hitting Grendel's mother in the neck, and this kills her. Beowulf rejoices and spots Grendel's dead body. He cuts off his head. The men greet Beowulf and they bring the head back to Hrothgar.

Following the death of her son, Grendel's mother attacks Herot, kills Esher, and flees with her son's claw. Beowulf follows the monster to the entrance of her lair, which is at the bottom of a dangerous, monster-infested lake. He proceeds to put on woven mail armor to protect him from Grendel's mother's claws and leaps into the lake with Unferth's sword named Hrunting. Grendel's mother then grabs onto Beowulf and drags him into her underwater lair, which is actually a battle hall.

Beowulf initially strikes Grendel's mother's head with Hrunting, which does not harm the monster at all. He then throws away his ineffective sword and proceeds to fight Grendel's mother with his bare hands. The two engage in a long struggle, and Beowulf begins to tire. When Beowulf stumbles, Grendel's mother manages to stab him with a knife, but his chain-mail saves his life.

Beowulf then spots a magical ancient sword from the days of the giants on the wall of the battle hall and uses it to kill Grendel's mother by striking her in the neck with the sword. After Beowulf kills Grendel's mother, he proceeds to decapitate her and swims to the surface of the lake.