Ah you have the international version so they have dark aeons lying around each place. I heard they're pains in the ass, don't know any strategies for them. Just be careful when you play, They're all over the place. Like if you go back to Yunalesca's area for Tidus' weapon enhancement you're going to fighting Dark Bahamut, for instance.
Nope, it's just the normal version o.0
And you are right, they ARE a pain in the ass, Valefor was very powerful, I'll just have to avoid them.
Go hunt for dark matters, get the limit break. :P
What are dark matters? What limit break exactly?