The beginning of this epic poem gives a very clear description of the fate of those who were in Hrothgar's hall when Grendel attacked it. The very first time that Grendel, who is described variously as a "grim spirit" and the "enemy of mankind," attacked the hall, he carried off with him various soldiers to feast upon in his lair, as the following quote makes clear:
Then he found therein a band of nobles asleep after the feast: they felt no sorrow, no misery of men. The creature of evil, grim and fierce, was quickly ready, savage and cruel, and seized from their rest thirty thanes.
After Grendel has repeated this visit a number of times, the narrator reports that Hrothgar's hall stood empty for twelve winters, because all who entered there met a similar fate. It is therefore assumed that few soldiers were brave enough to enter his hall because of the grim and grisly way in which Grendel slaughtered all who entered there. Until Beowulf arrives, few have enough courage to risk their life and nobody has enough strength to vanquish Grendel.