Possible Clues:

• Norse text where snake briefly recalled
• Mediaeval work suffered damage, lots missing
• Books of past and series of unremembered days
• Snake endlessly turning up in Old Norse poems
• Editor with deal, oddly, for literary collection
• Snorri's story
• Collection of ancient Norse poems
• 13th-century Icelandic book
• Old works inspected daily but not completely
• The Poetic __, a collection of Old Norse poems