Wikipedia: “Grendel is one of three antagonists, along with Grendel’s mother and the dragon, in the Anglo-Saxon epic poem Beowulf (AD 700–1000). Grendel is usually taken to be some kind of monster, though this is the subject of scholarly debate. In the poem, Grendel is feared by all but Beowulf.” This rifle conversion is called Gendal. Close enough.