What is the name of the evil monster/antagonist in Beowulf?

Beowulf falls into two parts. It opens in Denmark, where King Hrothgar’s splendid mead hall, Heorot, has been ravaged for 12 years by nightly visits from an evil monster, Grendel, who carries off Hrothgar’s warriors and devours them. Unexpectedly, young Beowulf, a prince of the Geats of southern Sweden, arrives with a small band of retainers and offers to cleanse Heorot of its monster. Source: https://www.britannica.com/topic/Beowulf