Final Fantasy XIII-2 is everything you could ask for in a sequel. Thanks to its new open-area environments (read: Knights of the Old Republic, Final Fantasy XII) you'll have plenty to explore beyond the main area. It's no Skyrim, but then nothing else is.
While most of the game's locations are populated by monsters both normal and rare, there are up to 8 Secret Monsters that you can find spread throughout the world. You don't fight them, but you'll definitely want to acquire them if you're a completionist.
To find them, you'll need your Moogle to use his Moogle Search skill. Doing so can be a real pain in the ass, so Japanese gamer Hsypersakura has put together a video which contains each and every secret monster location for easy "ITEM GET" acquisition.
He warns that each of these Secret Monsters can only be acquired once throughout the whole game, so don't delete them or trade their abilities with any other monster or you'll lose them for good.
