Return of the King

Harry died at Hogwarts facing Voldemort, in the afterlife he find out information about his life which should have occurred and he is pissed. He decides to go back in time with a new identity. Hadrian Merlin Pendragon, King of Avalon and of all Britain. His mission is to stop Voldemort before he comes into power, and enlist the help of the Sisters Black and other friends.