PAL version is the European release of the game, ie. Dark aeons aren't in the NTSC version released in the USA. I think that's right. ^^

They are not the same as the aeons you use at the end of FFX, they're not related at all really. Dark Aeons just appear in a few places near the end of the game (after the airship? I don't remember). They are difficult and mean and you need to at least get break damage limit to have a chance with them ;_; If you search for dark aeons in this forum, you can probably find a lot of threads with more details on them =)