Well third year was so boring that I won't tell you what happened in detail. Only Professor Lupin managed to stay as the DADA professor. Also I picked up Ancient Runes, Arithmancy, and Care of Magical Creatures. Oh I managed to clear Hagrid's name and he was allowed to resume his education. He is sitting his OWLs this year.
Now I could of been entered into the Tri-Wizard Tournament. However Sirius as my magical guardian put his foot down and invalidated my part in contract. It seems that whoever wanted me in did not count for a little known loophole that magical orphans like me that are the last of my line are immune to contracts that will spell the end of the magical bloodline.
I managed to join Cedric's support team. I helped him out with the idea of prepping a bag of goodies to summon from one of my house-elves that will be flying on an elf sized broom near the arena. All he needed to do is summon the bag and trick the nesting dragon that he is there to help her. He got a perfect score for the task. By the end of the first task the real culprit was found to be headmaster Igor Karkaroff as he lost his magic the moment the words this concludes the first task.
The clue for the second task saw Harry and Cedric take a bath together in the Prefects' Bathroom. There they figured out that it will be the traditional damsel rescue but under the black lake. So he managed to learn how to cast some aquatic spells silently. He got in and back out with Cho within half an hour.
Now I managed to intercept the port-key that would of taken Cedric out to a graveyard in Little Hangleton. I managed to ask Madam Bones to assemble a full squad of Aurors and use the rope port-key. She did three better. By bringing three teams with her.
By the time they arrived I managed to trap the last soul peace in the black soul gem. They where helpful in overpowering Riddle. But in the end I soul trapping him. Which had an odd effect on his branded followers. As the almost seven baker's dozen black soul gems I had with me was automatically filled on his death. It meant that all his brand followers died when he died.
I used all but the three dozen strongest to charge Hogwarts central ward-stone to overflowing. Which meant that Hogwarts will be finishing it's overhaul in a matter of days and still be slightly over full power.
I managed to use the Room of Requirement to download as much knowledge as is safe. After it helped me improve my mental defenses. So the following year I managed to pass both my OWLs and my NEWTs. I also got as much material on all my muggle subjects and lacrosse as my elves could get their little hands on. So I can learn them using the same technique.