Information:  - Sonatorrek ( `` the irreparable loss of sons '' ) is a skaldic poem in 25 stanzas by Egill Skallagrímsson ( ca . 910 -- 990 ) . The work laments the death of two of the poet 's sons , Gunnar , who died of a fever , and Böðvarr , who drowned during a storm . It is preserved in a few manuscripts of Egils saga Skalla - Grímssonar , ch. 78 . According to the saga , after Egill placed Böðvarr in the family burial mound , he locked himself in his bed - chamber , determined to starve himself to death . Egill 's daughter diverted him from this plan in part by convincing him to compose a memorial poem for Böðvarr , to be carved on a rune - staff .  - An eponym is a person, place, or thing for whom or for which something is named, or believed to be named. For example, Elizabeth I of England is the eponym of the Elizabethan era.  - A protagonist is the main character in any story, such as a literary work or drama.  - Egill Skallagrímsson (c. 904c. 995) was a Viking-Age poet, warrior and farmer. He is also the protagonist of the eponymous "Egil's Saga". "Egil's Saga" historically narrates a period from approximately 850 to 1000 CE and is believed to have been written between 1220 and 1240 CE.    Given the paragraphs above, decide what entity has the relation 'instance of' with 'literary work'.
A:
sonatorrek