Why does the dragon assault the geats in the epic 'Beowulf'?

a runaway slave stole a golden cup or goblet from the dragon’s treasure hoard, which made the dragon angry and desirous of revenge on humans (as the dragon realized the a human had stolen the goblet). read more

When the angry dragon mercilessly burns the Geats' homes and lands, Beowulf decides to fight and kill the monster personally. He and his thanes climb to the dragon's lair where, upon seeing the beast, the thanes flee in terror, leaving only Wiglaf to battle at Beowulf's side. When the dragon wounds Beowulf fatally, Wiglaf slays it. read more