It was a rather pleasant day, Luna Lovegood noticed as she walked into the familiar hustle of the platform nine and three quarters. She saw a few familiar faces and a lot of new ones. Her gaze caught Hermione, the smartest witch of her age, straightening her robes with one hand and dragging a gigantic trunk behind her in the other. Hermione waved at her as she caught her eye, Luna smiled with her usual nonchalance. They boarded the Hogwarts express together.

As both the witches moved in silence searching for an empty compartment, Luna noticed Hermione stop abruptly at what she assumed was a familiar voice. She looked curiously behind her shoulder to see none other than the Slytherin that took it upon himself to wear an evil, stereotypically Slytherin, mask around people, as Luna had noticed on so many occasions, he cared the most about. She couldn't help her slight surprise at the almost smile, he gave the flustered first year in front of him. Hey, was that really even a smile, or were the Nargles messing with her head again? Luna was pretty sure it looked dangerously close to one.

He actually smiled at the girls, (she must be losing her marbles!) to which, Luna easily smiled back, unlike her peers, she could always see through the resolute mask of pureblood supremacy the bloke always wore. Hermione, on the other hand, flushed a little (momentarily only, as the Gryffindor queen was always the undaunted warrior), but recovered quickly to give him somewhat of a straight smile, to which the Slytherin tipped his head.

Also unlike many people of their year, Luna never failed to notice the way the Slytherin looked at Hermione when he thought she wasn't looking. Luna was also pretty sure she noticed the almost nervous habits of the Gryffindor, albeit uncharacteristic of her, that she hid so well. Like that impossibly imperceptible smile she gave the Slytherin when he wasn't looking her way, the one she gave him the minute he turned his head just now.

Unlike their earlier years, Luna thought, they reached Hogwarts relatively quickly. Having already had changed into their uniforms, they made their way to the Thestral-driven carriages that took them to their school. It was a little tragic how a lot of people could see the Thestrals now, compared to the previous years.

As they made their way to the Great Hall, their were a lot of questions on the students' minds; "What's Hogwarts gonna be like, without Dumbledore?", "Will we still be able to play Quidditch?" , "Who will replace Professor McGonagall as the head of Gryffindor House?" , and the most interesting one, Luna agreed, "Who will teach Defence against the Dark Arts this year?". They hadn't had a permanent, or even consistent, DADA professor since their first year at Hogwarts. And considering the efficiency with which, McGonagall had taken headmistress-ship of the School, every one expected their new DADA professor to be relatively stable.

Luna was looking forward to meeting a new teacher very much, she was always curious to the notion that the job may be jinxed, now with Voldemort gone and everything, this will be their first actual chance to find out.

Professor McGonagall's start-of-term address was quite different from what Professor Dumbledore's used to be, Luna noticed as , like many other students, she too had the realization, that after about half a century, Professor Dumbledore was no longer the headmaster of Hogwarts.

[REST OF THE SPEECH TO BE ADDED]

"... And now for the question all of you have evidently been waiting for. Your new Defense Against the Dark Arts Professors!..."

"Wait a minute, did she say professors, more than one? How does that work?", Luna heard a Ravenclaw wondered aloud from two seats away. "Wait, listen, she's still talking!", someone shut them up.

"... It is something that has never been tried at Hogwarts before, but as the events of the previous year prove, it is about time that our students get practical training. Keeping that in mind, it is due to the constant hard work and untiring efforts of your teachers, that these professors for Defense Against the Dark Arts could be provided to you, they will teach you practical defense when encountering dark wizards in addition to wards and protections you can use to make places safe from intrusion. They also hold expertise in dealing with various dangerous magical creatures. Students please welcome, brothers Sam and Dean Winchester and their friend Castiel."

The students' gaze automatically shifted to the three men in muggles' clothes, entering the Great Hall, a look of pure wonder gracing their features.

-•••-

It was a normal day at the Men of Letters bunker, or as normal as it could get for the Winchesters anyway, as Cass popped out of nowhere. Or Sam always liked to put it, Apparated out of nowhere, right inside the Library door.

"Dean! Sam!", Cass called out with a slight note of urgency in his voice. "Cass, is everything okay?", Dean said as he leapt up from his seat instinctively. If he wasn't worried about Cass, Sam would've smirked.

"Yeah Cass, what's wrong?", Sam looked at him with concern.

"I..uh... a friend of mine...requires some assistance from us", the angel seemed a little nervous, Sam noticed with a little worry, what could make a ferocious Angel of the Lord nervous?

"Friend? Cass, what friend? What happened, is everything okay?", Dean asked concern etched into his features.

"Well, a few days ago, I was in the archives retrieving an archaic volume for Sam's research, when...I was...uh.. Summoned"

"Summoned? By who?"

"I was summoned to...another... Time"

"Wait, what?", the older Winchester asked, a little confused.

"Dean, don't forget, he's an Angel, he can not only reach anywhere on earth, but also anywhen, as in, anywhere in the space-time continuum", Sam clarified.

Dean rolled his eyes at the "nerdy" explanation and continued, "So what happened? Who summoned you?"

"I am of the opinion that it may have been unintentional, they probably summoned me without wanting to do so. They were, in fact in the need of assistance, although. They were at War! As my brothers always insist, that that's all humanity is capable of..", the angel dipped his head momentarily and looked up, visibly flinching at the look of indignation on the older Winchester's face, "Dean, that is not my opinion, but merely that of my brothers', I have come to learn how much humanity really is capable of", the angel gave the hint of a smile, that was laced with affection. Dean readily reacted to it by beaming positively at the angel.

Sam, once again, resisted the impossible urge to smirk.

"So is it the war they need our help with? Cass, people have been fighting wars since humanity first inhabited earth, you of all people know that", Sam brought the topic of the conversation towards the matter at hand.

"No Sam, the war had ended, that's not the point", Cass continued, "It's something else entirely"

"What is it Cass, you know you can tell us", Dean urged the angel to continue further.

"I...uhh.. Don't know how to...", the angel halted mid-sentence, staring at something behind the brothers, he tilted his head, as if in contemplation.

Before either Winchester could stop him, he crossed the room to the small shelf Sam had put up in the corner insisting All books belong in the same place, and retrieved a hard-cover book from the top rack, and held it up, title towards the brothers. Both the hunters graced him with look of what-the-hell-is-this-supposed-to-mean.

The angel looked at the cover, as if to check if it was the one he had intended to pick up in the first place, then spoke, "Hogwarts", he stopped after the single word, but continued after noticing the lack in change of the Winchesters' expression, "The headmistress of Hogwarts requires our assistance", the angel stated matter-of-factedly.

"Cass, that", Dean said pointed towards the book in the angel's hand, "Is a work of fiction! It's not real!"

"Dean, you don't understand, this is not a fragment of my imagination, I really did meet the headmistress of Hogwarts, and she did request our assistance, well my assistance, but I can not perform this task on my own"

"Wait, so we're going to Hogwarts?", Sam practically screamed after he managed to pick his metaphorical jaw off the floor.

"Yes, to put it simply, we are going to Hogwarts"

Sam squealed, Dean had to admit, it looked quiet horrifying to see such a gigantic man make that sound.

"We. Are. Going. To. Hogwarts!", Sam screamed barely being able to control his absolute glee.

"Is he alright?", Cass asked Dean with pure concern in his voice at Sam's unexpected behavior. "Don't worry, he's just being a nerd!", Dean chuckled.

-•••-

After the initial shock was over, Castiel explained to them that the headmistress of Hogwarts, Professor Minerva McGonagall, had requested him to be the new Defense Against the Dark Arts teacher for her students. Castiel had explained that he was not used to human behavior, customs, norms or expected social behavior, even of the timeframe he had spent almost eight years in, let alone about half a century before that. After some coaxing he had decided to take the position along with his human friends, the Winchesters.

The brothers, along with Castiel, then made some preparations for the place and timeline they were supposed to work in.

The older Winchester was thinking technically; what weapons they will need (if any, as Cass put it, "One does not require weaponry to inculcate the knowledge of the Defense Against the Dark Arts on young minds, Dean"), any research they might need ("You need to read the Harry Potter books, Dean!", Sam explained, looking exactly like an overexcited puppy), and of course, the right mindset. Going to 19th century London wouldn't be the easiest Thing in the world, after all.

As soon as they reached Hogwarts, they were greeted by the Headmistress herself. Sam could not believe himself, the castle was magnificent, breathtaking, more than he could have ever imagined. He greeted Professor Minerva McGonagall with such respect and enthusiasm, his Stanford teachers would be jealous.

"I'm exceedingly grateful to you, Castiel, and of course Sam, Dean", Professor McGonagall began as she welcomed her guests, nodding her head towards each of them one by one, "for excepting our proposal for your assistance, it is highly valued"

Dean nodded back in respect and politeness, this place seemed nice he could stay here for a while, maybe even enjoy his stay. Sam still looked like a puppy, who has found a bone. He couldn't blame the kid, ever since Dean could remember, Sam used to draw a lightning bolt on his head, pick up a stick or a ruler, and pretend to be a wizard. He smiled fondly at the memory.

Cass and Sam were both chattering excitedly with the headmistress, she was explaining to them what basics they would need to know before they could teach (Dean preferred train) the kids.

They were shown around the school by the famous groundskeeper, Hagrid. (Sam vaguely heard Cass whispering to Dean how he would make a rather powerful vessel)

Hagrid was as huge and as polite as Sam had always imagined. (He frowned in Dean's direction as he heard a faint, "Now that looks like someone who could rival our little Sammy in the art of a 'Growth Spurt'", emphasis on little, followed by a chuckle).

-•••-

Professor Minerva McGonagall first met the angel Castiel through a rather fortunate stroke of luck. It was during the preparation for the battle of Hogwarts, that a very flustered Slytherin 7th year had messed up a warding spell. She believed it was nit the stress itself, but the constant yelling and nagging of the particular student's Ravenclaw partner that rather did it, but regardless of how it happened the were indeed in need of help at that time. And the angel had proven to be... well an Angel.

After the battle of Hogwarts ended, Castiel was shown their sincere gratitude. Professor McGonagall found him to be quite an interesting person, they shared a very healthy conversation on human history and culture, and how it changed over centuries.

"Well Castiel, what do you do about twenty years from now?", McGonagall said as she arranged some papers on the desk. Castiel, who was immersed in all the moving portraits in the headmistress's office, replied simply, "Me, Sam and Dean, we are hunters, we hunt the Supernatural"

"And what does that include?", the professor asked with peaked interest.

"Weapons of various forms, I suppose; spells, hex bags, guns with silver bullets, devil's traps and holy water for the demons, machetes to decapitate the vampires, exorcisms, salt and iron for the ghosts, sigils for the angels...", the angel explained.

The professor got struck with a brilliant idea. They hadn't had a consistent Defense Against the Dark Arts teacher for quite some time now. She considered the idea of giving the students a Defense Against the Dark Arts professor who wasn't even a wizard. It had it's risks, but she decided it was a risk worth taking. The students of Hogwarts went on to become Aurors and join the Magical Law Enforcement. They should definitely be given some practical training in the field.

Reaching her decision, she voiced her opinion to Castiel as, "How would you like it Castiel, if you could be of more help to us than you've already been?"

Castiel looked up, an expression of curiosity on his face, he squinted a little as he answered quite honestly, "It will bring me great honor to be of any more assistance"

"Well then you will not object to taking the position of the new Defence Against the Dark Arts teacher for our students, now will you?", Professor McGonagall enquired.

Castiel looked blank at first, but slowly understanding the meaning of the enquiry, explained to the headmistress how he was not the best person for the position, as he was not only quite inept in the "People Skills", but also the fact that it had taken him about a decade to understand the norms and human behavior of the Winchesters' timeline, it may take at least the same amount of time, if not more, for him to adjust to a completely different geographical location and timeline.

Professor McGonagall suggested that he could be trained by the expert teachers and staff workers at Hogwarts very well.

In the end of the short debate about the ability of an angel of the lord to adjust to human behavior in two completely different locations and timelines, Castiel proposed to inviting the Winchesters with him to Hogwarts.

Professor McGonagall readily agreed, accepting the fact that the Winchesters were obviously the experts in the field.

And now she was welcoming the brothers along with their socially awkward angel friend to Hogwarts School of Witchcraft and Wizardry.

-•••-

After they'd been shown around the school, Professor McGonagall introduced them to the four heads of the houses; Professor Flitwick of the Ravenclaw house, Professor Sprout of the Hufflepuff house, Professor Slughorn of the Slytherin house and Professor Lupin of Gryffindor house, who was joining the school again this year, this time as a Transfigurations teacher.

Sam felt honored to have the opportunity to meet such legends. He conversed excitedly with all the teachers.

The teachers, Professor McGonagall explained, were to teach the in the art of Wizardry. A recent innovation in wandless magic was made which enabled magic-less people, or muggles, to practice limited amount of magic, a few essential spells and two or three important potions. The teaches will put this very technique into action while enabling the Winchesters and Castiel to become effective Defense Against the Dark Arts teachers.

Sam could have never imagined what happened while they were practicing wandless charms; Dean had Professor Flitwick's wand in his hand as the professor demonstrated wandless administration of Wingardium Leviosa, he gently waved the wand absent-mindedly and sparks flew from the wand. Sam could not believe his eyes, actually he didn't until he heard Dean exclaim, "Holy shit, Sammy! I'm a WITCH!"

Sam replied automatically, "No, that's not how it works, you're a wizard, Dean!"

None of them quite understood the snicker that came from the angel, who composed himself instantaneously.