The Geatish warrior killed and devoured immediately before Beowulf fights Grendel is Hondscio.
Hondscio is one of the Geatish warriors who accompanies Beowulf to Heorot, King Hrothgar’s hall. When Grendel attacks the sleeping warriors, the monster seizes Hondscio, kills him, and devours him before Beowulf confronts Grendel directly. Beowulf then grasps the monster in the famous hand-to-hand struggle that ends with Grendel’s arm being torn away.
Hondscio has only a brief role, and his name appears just once in the Old English poem. That limited appearance makes him easy to overlook, but his death establishes the immediate horror and danger of Grendel’s attack before the hero’s battle begins.
Oslaf and Yrmenlaf are other names associated with the poem’s wider warrior world, while Wulfgar is a Danish herald who greets Beowulf’s company. None is the warrior Grendel consumes at this point in the story.