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.    What entity does 'sonatorrek' has the relation 'instance of' with?
A:
literary work