Quote Originally Posted by Aerith's Knight View Post
Oh, perhaps I know. It's in Midgar, Shinra headquarters. There's a puzzle on floor 67 or something, where you have to crawl through ducts to get 2/3 items, which includes an all-materia. But you can never get all 3.
It's a Star Pendant, Four Slots and an All materia. You can definitely get all three though.

Still worth a shot though, especially with the ducts clue!