The Phoenix

"I decided to keep the horcrux, so that I might make better use of it. Have you ever heard the expression, Miss Granger, that it is better to fight fire with fire?" "You can't be serious, Professor, that's reckless, its-" "I'm quite serious, Miss Granger, it's the one thing he would never see coming." Tomione, canon compliant through Half Blood Prince, and AU thereafter.