Final answer:
The literary device used to describe Grendel's actions in the tale is hyperbole, an exaggerated form of description to emphasize horror and strength, making the story more vivid and impactful.
Step-by-step explanation:
The literary device used in the description of Grendel "blundering back with the butchered corpses" is a form of hyperbole. Hyperbole is a rhetorical device in which statements are exaggerated to create a strong impression and is not meant to be taken literally. This use of hyperbole in the story serves to create an exaggerated sense of horror and emphasize Grendel's monstrous strength and brutality. These extremes help to make the encounter with Grendel more vivid and memorable for the reader, contributing to the epic nature of the tale. Authors use literary devices like hyperbole to render stories more immersive, by highlighting certain characteristics and adding to the overall impact of the narrative.