Beowulf faces more challenges in fighting Grendel's mother than he faced in fighting Grendel. First, Beowulf had to go to Grendel's mother in her lair rather than waiting for her to come to him like he did with Grendel. Her lair was at the bottom of a lake that teemed with monsters and burned at night. The lake was so deep no one knew how deep it was. While Beowulf was able to grab ahold of Grendel, Grendel's mother grabbed ahold of Beowulf when he arrived in her lair. Also, Grendel's mother's skin was so tough his sword would not cut it so his blade was useless. She appears to be stronger than her son, too, because she manages to put Beowulf on his back and she sits on him. She claws at him and stabs him with her own blade but he is saved by the chain mail that he wears. Finally, he sees, "..hanging on the wall, a sword hammered by giants, strong and blessed with their magic, ...". With that sword, Beowulf is able to cut off Grendel's mother's head.
Grendel's mother has already done away with several worthy warriors. She is especially enraged by the death of her beloved son, making her all the more dangerous.
As for Beowulf, he has to not only overcome her physically, but he must also resist temptation by not becoming too enamored with the bountiful treasures the monster has hidden in her watery cave. Beowulf “carried no spoils from those quarters / except for the head and the inlaid hilt / embossed with jewels; / its blade had melted / and the scrollwork on it burnt, so scalding was the blood / of the poisonous fiend who had perished there” (1612-1617).