In that scenario he could become a closed timelike curve: go back, become the being that invented magic in the first place, and program it to record the brain states of everyone at every moment in there lives for future recall given a spell or ritual that he would then know. This could also explain the "Atlantis erased from time" business. It would rely on magic changing the laws of physics in a way that allows magic time travel to operate before magic existed - or for the invention of magic to have happened outside the timestream.
New chapter, and the end is now in sight!
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 103.
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: