"Let's assume Dumbledore knew fiendfyre could be used to destroy a horcrux. Potentially one of the only other ways to destroy one. He needed a reason for Draco to complete the transition but it would be suspicious to have him do it alone." Hermione’s words flowed quicker now, as her brain leached onto the possibilities. "What if he knew I was his soul bond? By adding me into the animagus process it ensured Draco would eventually defect and join our side. If we weren’t in that dungeon together so often this past year - we may have never found each other. He had you come along too because you're his best friend and arguably - receive better grades. Our grades were a cover and since Luna’s on parr with Draco, she got thrown in the mix."