Beowulf begins with the story of Hrothgar who built the great hall of Heorot to protect his people. When the land of these Danish people is afflicted by the threat of Grendel, a horrible monster who wants to destroy the land, Beowulf comes to the aid of the Danes. After Beowulf defeats the “invincible” monster, Grendel's mother takes revenge on the land. In the first two battles of the story, the theme is to right the wrongs committed against them by killing their enemies. This cycle of revenge is started by the monster Grendel, descendant of Cain, the first murderer who killed his brother in revenge for not being favored by God. Grendel hates the mead hall that the Danes built and their nightly feasts with songs , then takes revenge by terrorizing the citizens.