Charles Phantomhive entered the HP world. He was Albus's senior, Severus' teacher, and an original character in the eyes of those who traveled through the Harry Potter era. On the surface, he is the backbone of the Order of the Phoenix, but in fact, he quietly watches the show behind the scenes and occasionally changes a little bit of history.
This article is about plot, British style, slow-burning, and I don't want to get into it by mistake.