In Beowulf, Beowulf first kills the monster Grendel.
The episode begins after Grendel has terrorised King Hrothgar’s Danish kingdom for twelve years. The creature repeatedly attacks Heorot, the king’s great mead hall, killing warriors while they sleep. Beowulf, a hero from Geatland, hears of the suffering and sails to Denmark with fourteen companions to help Hrothgar.
Beowulf chooses to fight without weapons because Grendel does not use a sword and because he wants the contest to be a direct test of strength. During the night battle, Beowulf grips Grendel so powerfully that he tears the monster’s arm from its shoulder. Grendel escapes to his marshy lair and dies there; Beowulf displays the severed limb as proof of victory.
The first victory leads directly to the poem’s next major conflict. Grendel’s mother attacks Heorot to avenge her son, forcing Beowulf to pursue her into an underwater lair. Much later, when Beowulf is an aged king, he fights a dragon. The Minotaur, Caliban, and Smaug belong to other mythological or literary traditions, not to the original Beowulf poem.