Engagement necklace

The engagement necklaces are important items in the Final Fantasy XIII trilogy. They are symbol of eternal love and devotion to the lover between Serah Farron and Snow Villiers.

Final Fantasy XIII
One day before the fireworks, Snow and Serah went on shopping to buy birthday presents for Lightning. During that time, Snow slipped away from Serah and went to buy two necklaces in the shape of Cocoon and use them as a means of proposing marriage to Serah next day.

On the day of fireworks, Snow proposes to Serah on the pier to which the girl agrees.

Final Fantasy XIII-2
After Lightning's disappearance after the catastrophe, Serah was believing that her sister was alive and not encased in the crystal within the pillar supporting the shell. Two years after that event, Snow says that he believes Serah and sets out to search for his fiance's sister handling his engagement pendant to Serah asking her to keep it and promising that next time they meet it'll be with Lightning.

Year later, Noel arrives with message from Lightning to take Serah to Valhalla and use a time gate to do so, but they need to use an artefact to open the gate. While searching for an artefact, Serah and Noel chase after Rhett who stole something' from Maqui. During the conversation with the boy, he reveals that he took Snow's engagement pendant from him, handles it over to Serah, and quickly runs away.

When the two are about to three, it is revealed that Maqui made a new chain for the necklace.

Lightning Returns: Final Fantasy XIII
After Lightning appears in the Grand Palace of Yusnaan, Snow is surprised to see her. Few moments later they clash, but thanks to Lumina, he quickly gets away and Lightning is forced to chase him. Along the way, Lightning comes across locked door which Hope isn't able to unlock an is forced to retreat to the Ark.

When Lightning once again reach the Grand Palace and continues her pursuit of Snow, she comes along the ice-covered door and after looking for a way to open it she finds Serah's engagement necklace. Snow reveals that he fought that Lightning is fake and left Serah's necklace as a means of opening the door. If she was truly a fake, then she'd never consider to use the keepsake to unlock the door. After the two battle, Snow starts to turn into Cie'th and Lightning tries to talk sense into him. After she is threw away with Snow's blow, she picks up the necklace she dropped and approaches Snow once again speaking to him about Serah. Few moments later his soul is saved.