Despite what nearly everyone thought, Sirius Black decided, there was, in fact, perfect justice in the Universe. After all, good, bad or in-between, whatever fate the Headmaster had planned out for Harry, and for Sirius, he would be experiencing himself.
Oh, it wasn't justice for him, granted. In fact, it was downright annoying going from being 21, in the prime of his life, to being over 100 years old with creaky joints, grey hair, and an inability to pursue all the lovely of-age Seventh-years. But compared to where he could be, it was outright divine grace.
The irony that he had to find Peter and put the traitor on ice instead of revealing his innocence made him smile. Must keep that bastard Sirius Black locked up! Hogwarts undoubtedly had somewhere you could store a rat with periodic doses of the Draught of Living Death, attended occasionally by a house-elf. He would try to find out where the Chamber of Secrets was. Clearly, the "former Headmaster" had not given a damn about anything.
Xeno, to whom Sirius owed a debt he could never repay, had convinced him to change as little as possible from the "history" of the next twenty years. They had negotiated terms when Sirius pointed out that meant twenty years of stunting and shortchanging young, innocent boys and girls.
The compromises they'd hammered out included Binns still being there by the time Harry arrived, but a real history teacher teaching most of the lessons, with Binns tutoring advanced students in his speciality of the Goblin Rebellions. He'd free Trelawney, and get her cured of her taste for drink at St Mungos. She could still be flamboyant and obnoxious, but would teach everyone the correct facts about Divination, and tutor those with the gift.
Sirius remembered meeting with the centaurs. Young Firenze had stared at him, in silence, for several minutes. The rest stood a little apart from him and waited for him to speak.
"You are tampering with what must not be," he finally sighed. "We saw Mars was bright, and before our eyes, it dimmed."
"Well, this is awkward," Sirius had said. "I heard there was an exceptional diviner among you, and I was going to ask you to occasionally assist Ms Trelawney."
There had been another long silence.
"This man is a passive victim, tossed one way, then the other, by those with the hubris to challenge what is written in the stars. If we interfere, only now, justice will be thwarted." The other centaurs had no expression as they turned about and galloped off.
"Her I will assist, young Black. But never you; you are already clouding the future like nothing we have seen before. Go." With that, Firenze, too, had galloped off.
He would ease Snape out of the castle, strengthening the wards against the dark mark over time. He would move his cousin, Andromeda, in as Potions teacher and Slytherin head, and pay Sluggie whatever he needed to take on the senior students as a part-time instructor. Doing that, of course, meant easing Lucius off the board so he could tell Snape he was being forced to bow to pressure from them. Eventually, Snape would do his potions and research in the Shrieking Shack, refitted as a potions lab. The irony soothed Sirius's soul.
Andromeda was the most important person in the world to him, right now. He would make sure her daughter Nymphadora got good treatment when she arrived there in a few years. She was a delightful child, but metamorphmagi like her tended to have a hard time in their younger years.
While the headmaster was still in shock, still reeling from his reversal of fortune, for he had believed he was about to be free from the Dursleys, Andromeda had visited him and laid down the law; if he gave her the power to act for the Black family (some of the paperwork she had him sign reinstated her and her daughter), she would arrange to have newspapers and periodicals sent to him once a week. Sirius had banked on the old man wanting as much information as possible to plan his escape or comeback. After hearing all his protestations that he was really Albus Dumbledore, who had been living in Harry Potter's body for ten years, Andromeda had replied, "Well, it's a relief to learn why you did it, Siri. In ten years, I think we'll put you next to the poor Longbottoms, shall we? The James Thickey ward - it's a nice place, much nicer than here. Sign here, too, please. And here, and over here. Thank you, who's a good boy?"
He would confer with curse-breakers about the one on Defense Against the Dark Arts. Covertly, he would tell applicants for the position that he believed teaching more than one school term in succession would invoke the curse, so they could teach, leave and return. To outsiders, it would look like it was still in place, but there would be no harmful effects to the hired teachers.
Every child in the Black family had had some Alchemy lessons beaten into them. Teaching an introductory course in it once a week would introduce him to the students on a personal level and keep his mind occupied. It would also confuse anyone who was otherwise catching on; people untrained in Alchemy thought it was impossibly hard; in reality, it was about as difficult as enchanting. And it was firmly associated with the Headmaster in the public mind.
He would change the DADA curriculum over a year's time to include physical training, he decided. And get Slytherin under control. If he remembered correctly, young Stan Shunpike was going to go to the bad right about now, under Snape's misdirection. The latter, newly hired Death Eater hadn't even met his first student. He couldn't lie about the Board yet; probably pulling something out about the Hogwarts charter or Ministry pressure would induce Snape to at least adhere to some rules. It would amuse the Black family part of his personality to let Snape cry on his shoulder over having to do even a quarter of his job.
It was a good day today. He'd managed to combine the Headmaster's famous twinkling effect with a spell that made his eyes track in one direction while he focused on another.
Oh, those Seventh Years!