Ovid created suspense in "Pyramus and Thisbe" by dragging on Pyramus discovering the fate of his love which was all untrue. He did this by using many sentences that eluded to this discovery, causing Pyramus' death. Suspense is further carried on by Thisbe now having to discover her lover close to death, promising her own downfall in the name of love.
Answer:
The line 'So Eden sank to grief' is an allusion, or literary reference, to the Biblical story about The Garden of Eden, a perfect paradise until Eve ate from the Tree of Knowledge. By making this reference, Frost is implying that the idea nothing good can last is an old one; it's part of our human experience.
