When grendel says hrothgars waariors became hornets what literary device is being used?

The literary device used when Grendel describes Hrothgar's warriors as "hornets" is a simile.

A simile is a figure of speech that compares two unlike things using words like "like" or "as." In this case, Grendel is comparing the warriors to hornets, emphasizing their aggressive and swarming nature. This creates a vivid image in the reader's mind and also helps to highlight Grendel's fear and hatred of the humans.