HP: Azkaban's Outstanding Graduate

[HP fanfiction] [No female lead] [Has followers]
Sargeres Greengrass is a time traveler, a member of a pure-blood family in the wizarding world. His first experience with magic came from his mother's Cruciatus Curse, but when he sought his father's help, he discovered that his father was a Death Eater.
Five years after being expelled from Hogwarts, Sargeras returned to the ancient castle as a professor, wading through the salty mist of the North Sea.
Azkaban's imprisonment did not leave him with madness and decay, but rather with a kind of chilling elegance.