Karl Kopinski is an artist famous for him interest in Norwegian legends. He is especially popular for his interest in Beowulf. This picture can be found in stores around the world. It refers to Beowulf's fight against Grendel and his mother.
After Beowulf defeated Grendel by ripping off his arm, the arm was hung from the rafters as a trophy and proof of Beowulf's victory. This occurance was the reason for the second battle, where Beowulf fought against Grendel's mother.