Walk of Time - We're in the Void Beyond again, though this time you control Serah only, and Mog is kinda out of commission too (he can only do Moogle Hunt with R1). Walk east until you spot a familiar figure...
Talk to her for a Live Trigger: (Serah's trapped in the shade of Valhalla. Yeul seems to know something...) and you receive the VOID BEYOND FRAGMENT - Etro's Sorrow (01/05) + 600CP! She moves further east, and upon discussion gives you another Live Trigger: (The goddess gave her servants the ability to see the future. What else does Yeul know?), as well as parts with the VOID BEYOND FRAGMENT - Pulse's Resolution (02/05) + 600CP! Collect the Live Trigger Cube behind you for a reward.
To your south is a treasure sphere with a Librascope, then go upstairs and loot another sphere for the Serah Mask (but only if the game detected a FFXIII save). That girl has moved between two sets of stairs now.
Chat with her for the VOID BEYOND FRAGMENT - Lindzei's Desire (03/05) + 600CP! Walk back downstairs to the east and talk to her again for the VOID BEYOND FRAGMENT - Mwynn's Tenderness (04/05) + 600CP! And finally walk upstairs to the Throne of the Goddess and talk to the girl one more time for the VOID BEYOND FRAGMENT - Bhunivelze's Sleep (05/05) + 600CP!
Dart west upstairs and press R1 near a concealed Chocolina, who amazingly sells nothing new. Hey, girl, shape up!
Talk to the elusive girl for the final time...
Boss Battle: Cauis Ballad (The Void Beyond)
It's Serah and her monsters against the boss. He retains pretty much the same moves from the first battle, and gains the ability to instantly remove an accumulated Chain Gauge called Chain Break, making it hard to achieve Stagger.
There are two trump cards you can bring in this battle - SEN monster with Mediguard, and Serah's SAB role. Stick Poison on the badass while the SEN monster draws the heat. Dispel the Caius's buffs as they appear and ensure Poison is always on.
PARADOX ENDING - After you beat the game, visit the Serendipity timeline. Enter the leftmost building and talk to the girl dressed as chocobo to unlock Paradox Scope fragment skill. MAKE SURE TO TURN IT ON! Use Time Reversal on AF4XX Academia timeline, give Alyssa five graviton cores, and proceed to the place of this encounter. When you begin the battle, the words "PARADOX SCOPE" appear on screen, and you will fight a stronger version of the boss. Defeat him for paradox ending (06/08).