Simplify the following text for a Grade 5 native English-speaking person.
Original: But the next night , Grendel 's mother comes to Heorot and kills many people for revenge and grabs Grendel 's arm .
Simplified: The next night , after celebrating Grendel 's death , HroÃ gar and his men sleep in Heorot . Grendel 's mother appears and attacks the hall .