Crusader is obtained after you defeat all eight Legendary Dragons.

Palidor is obtained by picking it up on the shore on Solitary Island.

Phoenix can be obtained by re-recruiting Lock in the Phoenix Cave.

Seraphim can be obtained by talking to a man standing behind a tree in Maranda, I think. Or Tzen.

Golem and Zone Seeker can be obtained by purchasing them in the Auction House.

Um, I don't remember them all right now.