The taster comes with a unique scenario featuring Lightning, as well as the ability to carry any in-game items plundered into the main game. In addition, you'll also unlock an Aerith assist character in the main game. So it's a kind of demo, that contains a very short stand-alone campaign and bonus content should you decide to upgrade to the full game. It's due out next week on the PlayStation Network, and will run you $2.99. Expect a similar price in Europe.
We're genuinely excited for duodecim, but we're really sick of typing that name. We're doing it out of principle now, mind. Stubborn lot.