Nabaat, Ultros & Gilgamesh, once bought, will have a chance to say "Final Fantasy XIII-2; the story so far," along with everyone else.
Additional story content:
"Heads or Tails" (Sazh's story) — Explains Sazh's sudden disappearance and his attempt in finding Dajh through the power of fortune. Adds Sazh (Role: Synergest, Feral Link: Cold Blood) as a party member when cleared. Also unlocks two new Serendipity card minigames, Chrono Bind and Serendipity Poker.
"Snow: Perpetual Battlefield" (Snow's story)
"Requiem of the Goddess" (Lightning's story) — Story segment shown through Lightning's point of view as she struggles against Caius. Adds Valkyrie Lightning (Role: Commando, Feral Link: Legion of One) as a party member when the battle is cleared with five stars.
The "additional voices" section reads as practically a "who's who" of every major active voice actor out there that isn't already part of the main vocal cast, including pretty much the entire English cast of the playable characters of Eternal Sonata and many who had major roles in previous Final Fantasy' titles, such as Hedy Burress.
Final Fantasy XIII-2 was originally supposed to tie-in with Type-0 being set 900 years into the future still with Valhalla being in the year 999 (the same year Type-0 is set in) but the idea was cut. The idea of humanity being reduced to a single village stuck in a Time Crash was retained for Lightning Returns.