Is the blade of awe guardian only in AQ

Yes.


IMPROVEMENT:
Yes. However you can still collect the pieces as a normal free user, and choose to buy a guardianship later on. You will have the pieces, and won't have to worry about finding the blade when you do gain guardianship. I have the blade, and did this. Some places you can find it are:
Crossroads -> Somewhere.
Granemore -> Haunted house (you might have to beat it a few times.)
Rip in the Sky -> Library -> Click on floor panel.
hope i helped