It's the back of the latest Nanoha Sound Stage: The Strikers Sound Stage X, or simply SSX. A new enemy has awakened, using corpses infused with cyborg technology.
It's a Sound Stage focusing on the StrikerS cast, mostly Teana, Subaru and the numbers. You get to know what happened with the Numbers, what Vivio is doing, how Teana is doing in her job as an Enforcer, and so on. I really recomend this Sound Stage, its great.