Disclaimer: I do not own Harry Potter or any of the characters.

Original A/N: Thanks to MaeSilverpaws1, who is beta-ing this story.

Chapter One Hundred Twenty-Two

A Sirius Professor

Sirius was surprised that he felt a little nervous as he got ready for his first morning at Hogwarts as an instructor. He wasn't really sure why, it wasn't like he hasn't talked in front a number of people before. He has even been an instructor to the training Aurors before, but this felt different all the same. He was glad that his first lesson was with the first years. He could stumble all over himself and they wouldn't know the difference. He tried to remind himself of that as he walked down to the Great Hall, and as he ate his breakfast, but it didn't help him become any less nervous.

"Sirius? Are you all right?" Filius Flitwick asked.

"Huh?" Sirius replied.

"I think he's nervous," Aurora Sinistra said smiling at Sirius.

"I don't think I've ever seen you nervous before," Filius said amused.

"I don't think I've been nervous like this before," Sirius shrugged, he didn't mind the light teasing his colleagues were giving him.

"Well there's no need to be worried. I have every confidence you'll do well," Filius said.

"I bet you say that to all the new Defense professors," Sirius said.

"I have said it to a few," Filius eyes were twinkling with amusement again.

"But this time he really means it," Aurora said.

"Thanks," Sirius grinned at her.

Sirius wasn't sure if that talk really helped him or not, but he had no time to think of that now as it was time for his first lesson. He felt himself ease when he noticed how nervous the first years were. He just went into himself and started talking.

The rest of Sirius's day seemed to fly by. He had two more classes and by the end of them he felt like he had nothing to worry about. Still the next class was the one that he was looking forward to since he first agreed to become a Professor. He sat at his desk watching the fifth year Gryffindors walk into the room and take their seats.

"Hello everyone, I'm Sirius Black, and there's no need to take out your books," Sirius started, and gave Hermione a smile seeing as she was the only one that had taken hers out. "I'm not sure if you had the O.W.L lecture from your other professors yet …" he went on and judging by their reaction he added, "so I guess you have. Don't worry, I'm not about to give you another speech about how important this year is. You'll have quite enough of those this year without me adding to it.

"So instead, I thought I would start this class with discussing what happened last year … to be more process what happened with your last Defense professor … but first a little bit about myself." Sirius went on and heard a snort form the direction of Harry's table. Sirius glared at him and Harry gave him an apologetic look. "I've been an Auror since I got out of Hogwarts, I've taught a few prospective Aurors over the years, but I haven't got a clue about what I'm supposed to do now," Sirius finished confidently.

Harry snorted at that again, this time he was joined by several others.

"Oi Potter, stop laughing at me," Sirius frowned.

"Sorry Professor," Harry said, not able to keep the laughter out of his voice.

"Now let's get to the real topic of today's lesson, which is as I said what happened last year," Sirius went on, dropping his joking behavior. "Now everyone is aware that Barty Crouch Jr. was discovered to have impersonated Alastor Moody last year," he waited until he saw the students nod their heads. "Can anyone tell me how he was able to pull that off?"

Hermione immediately raised her hand but it seemed like everyone else wasn't sure.

"Sorry Miss Granger, but I think I need to answer this one myself," Sirius said to her, and he couldn't help but notice the slightly annoyed look she was giving him now. "The first thing that Crouch used was Polyjuice Potion … why don't you tell us what that is Miss Granger."

"The Polyjuice Potion is a potion that allows the drinker to assume the appearance of someone else," Hermione answered quickly.

"Correct," Sirius smiled at her. "Polyjuice Potion is one of the most dangerous potions there is. Not in the sense of physical harm of course, though the potion is not very pleasant when you take it. It morphs your body into someone else and that is not painless."

"Have you ever used Polyjuice Potion?"

"Yes, Mr. Thomas I have," Sirius answered, "I needed to impersonate a member of this gang for a few weeks in order to be able to arrest them. The only benefit about taking the Polyjuice Potion for a prolong amount of time is that it doesn't hurt when you still look like the person you're impersonating. It still tastes pretty bad though.

"Now what I was saying, though the Polyjuice Potion doesn't kill or harm people … it's not a poison after all … it still is one of the Darkest Potions there is," Sirius said. "If you need an example of that, just think of what happened last year. Mad-Eye Moody is one of Dumbledore's closes friends, and there was no way for even him to notice the difference between the original and the impostor. Physically there was no way to tell the two apart. Of course there are a few things that the potion couldn't imitate when it came to Moody. His magical eye for one, as well as his legs.

"There are other things that Polyjuice can't duplicate, as well as reasons why it won't work for certain people," Sirius went on. "It will not work on anyone that is more than a quarter giant, goblin, veela or any other creature that are able to mate with humans. It does vary depending on the creature. Giant for instances are the most resistance to magic in general and even several generations later they wouldn't be able to us the potion properly. Veela on the other hand are more receptive to magic so sometimes even half veela are able to use it, depending on the person in question.

Also the potion doesn't work with humans that have been changed, such as vampire or werewolves." Sirius made a face at his last word.

"Do you not like werewolves?" Lavender asked.

"Because Professor Lupin was the best professor we've had," Dean added.

"Not after this year he won't be," Sirius stated and then smirk, "actually Remus Lupin is my best mate. I have nothing against werewolves … just laws and prejudiced against them."

"But aren't there a lot of bad werewolves out there?" Seamus asked.

"Of course there are," Sirius answered. "Fenrir Greyback is the worst of the lot right now. He purposely tries to bite people, kids in particular and he's not opposed to killing them either. But I prefer to judge a man by his action and not what he is.

"Again, back to the lesson," Sirius said after his last statement had settled for a moment. "As I was saying about abilities, just because you physically become the other person with this potion you don't gain their capabilities. So that brings us to the second, and much more complicated, part of impersonating someone else. You have to learn their characteristics, the way they talk to people, the way they eat and drink … you have to learn as many of their mannerism as you can. Especially if you are using the potion for a long time. If you don't have the basic mannerism down, people will get suspicious of you even if they don't completely understand why."

"Does that mean Crouch acted like Moody would have?" Dean asked.

"Unfortunately for all of his constant vigilance preaching …"

"He really says that," Pavrati comment.

"All the bloody time," Sirius said shaking his head, "it's really annoying."

"Yeah," Pavrati agreed as did a few of the other students.

"Well, that made him almost easier to impersonate," Sirius explained. "He's very set in his ways and noticeable about it too. That made easier for Crouch to convince the masses that he was Moody. However, fooling Dumbledore, and others that have known Moody for years, was another story. The only way he was able to do that was by forcing the real Moody to give him information. I don't want to know what happened there, but for Moody to give up that much information it had to have been bad.

"Now as I see we only have a few more minutes left in this class," Sirius said looking at his watch. "And I can see that some of you might be wondering what this has to do with this class. Defense Against the Dark Arts isn't just about learning counter curses or other spell work. The Dark Arts is an ever changing ever evolving form or magic. As soon as you find one way to stop a curse, someone invents a new one … or worse they learn how to make a common spell deadly."

"Do you mean they could make Lumos deadly?" Lavender asked.

"Yes, that is what I mean, after all there is someone in this room that used the Levitating Charm to knock out a mountain troll," Sirius said.

"Don't look at me," Harry said when everyone looked at him and he pointed at Ron, "he's the one that did it."

"Bloody scariest thing I've ever done in my life," Ron added with a grin, "well at least until that point."

"That's not the same as Lumos though," Seamus pointed out. "How do you make Lumos deadly?"

"You can target your opponent's eyes," Sirius replied. "It wouldn't be a simple spell I would imagine by the time you make it truly harmful but the principle could stem from the Lumos Charm.

"Now our lessons are going to run similarly as they have today," Sirius said. "I'm going to bring up a curse, counter-curse or potion and we are going to have an open discussion about it. Like you had today, feel free to interrupt me if you have any questions or comments. The more you're involved in the conversation the more you'll remember. Most likely if we are discussing a curse or a counter-course the next lesson we have will be a practical one and we will learn what we had discussed. Depending on the difficulty we may spend a few lessons on the curse. Any questions?"

That question was met with silence.

"Good," Sirius said. "Now does anyone have any more questions about what happened last year?"

O

The next morning Sirius arrived at his classroom feeling really confident, only to feel his mood steadily turned darker. It was his first class with the Fifth year Slytherins and he felt like they were all watching him with judgmental eyes. He knew there were several children of Death Eaters in this room, and they likely would have heard of him before. He felt himself bristle and knew that his plan to lecture all the fifth years the same wasn't going to work for him. He had to find a way to work through his animosity toward a house he had never liked and somehow get the Slytherins to listen to him.

"I was going to start this lesson on the Polyjuice Potion and what had happened with Barty Crouch Jr. and Alastor Moody last year," Sirius started once the class started. "But I think it's more important for us to find a common ground.

"I'll start by saying I'm Sirius Black. I come from a long line of Slytherins and I was the first in two hundred and twenty eight years to be sorted into Gryffindor," Sirius stated. "For much of my time at Hogwarts I hated all Slytherins … particularly Severus Snape I might add. I actively tried to be separated from the rest of my family …"

"More like they wanted to be separated from you," Sirius though he heard.

"What was that Mr. Malfoy?" Sirius asked.

Draco seemed to flush, but he said, "The family wanted to be separated from you."

"That is true as well," Sirius agreed. "My mother in particular wanted to get rid of me, she even disowned me from the family. Unfortunately for her I was the only male Black so there is nothing any of us could do about me not becoming the head of the family when my father passed away.

"It wasn't until I was twenty-one that I realized that being a Slytherin has nothing to do with light or dark," Sirius said. "I was foolish as a boy, and I let my prejudice against pureblood elitists…."

"You're a pureblood," Draco said rolling his head.

"Yes I am, and my family is one of the most elite families around," Sirius said. "Are you going to argue about that with me, Mr. Malfoy?"

Draco just glared at Sirius.

"I did mention that I was a bit foolish," Sirius said. "I'm definitely proud of being a Gryffindor, it was the best house for me to thrive in, but I think I understand Slytherins more now. I will try to be as fair as I am capable of being. I encourage discussion in my class. This year it is very important for you to understand the reason behind the curses, counter-curse and potions that you would use or that would be used against you in our class. Feel free to interrupt me in my lecture at any point with question, concerns or comments. I want as many people involved with the conversation as possible so that I know that all of you have gasped the subject.

"Now does anyone have any questions for me?"

Sirius wasn't surprised at all that there was many questions for him. He would never claim that it was his favorite class, but he felt that he had come to terms, sort of speak, with them.