After Voldemort died for the final time, the DADA position was finally free of the curse. Harry Potter took it up at the age of 20 to 24, until he mysteriously ended up in the past. But he wasn't younger or lacking of any skills. He was still 24. And 11 year old Harry didn't exist anymore because it would cause a timeline collapse. At least, that's what Harry figured out after a Gringotts inheritance test, magic cleansing, and a name change. Now there's a hawk animagus taking up permanent residence at Hogwarts with the castle's permission and he plans to fuck Dumbledore over and fix Tom. Hadrian J Peverell the Eurasian Sparrowhawk has set up his roost and is not leaving.