Harry Potter and the Perversion of Purity

AU: Harry Potter was a naive, malleable child when he first entered the wizarding world. What if instead of meeting a good, noble family and being guided towards the light, he met a shadier bunch and was warped and twisted in ways that led to a much darker Magical Britain? Realistic, Dark Harry, Slytherin Harry, Good Dumbledore and Weasleys, Mostly In-Character Harry at the Start