On Thursday evening, as promised, I headed down the seventh floor corridor to the Barnabus the Barmy statue. Then, I paced in front of it three times, thinking "where the DA meet". I had a hunch this room was created on intentions, so I focused on not doing the DA any harm, on protecting them.

I had barely finished walking around the third time when the door formed, and I wrenched it open and entered.

There were already huge groups of students mingling around, chatting, but there didn't seem to be any specific order. However, I did note that I seemed to be the only Slytherin here - the rest of them were Hufflepuffs, Ravenclaws, and naturally, Gryffindors.

Feeling a little uncomfortable as people turned to stare daggers at my green and silver tie, and regretting the decision to not change into something else, I finally caught sight of Neville and Ginny, and approached them.

"Oh, there you are," Ginny said, studying me carefully. "Do you know what you're going to do today?"

I glanced behind me. They all seemed to hate me, so I needed to do something that would prove my loyalty to them and yet show how advanced my magic was so that they would finally allow me to teach them the finer points of duelling, which I doubted any of them had the heart to learn from me today. So I turned back.

"Do you know the patronus?"

Ginny nodded. "Harry's already taught us that."

I felt my heart sink. "How about using it to send messages?"

Ginny paused. Neville looked eager. "You can do that? That would make the DA communications system more secure."

Ginny nodded. "Good plan. ALRIGHT PEOPLE, LISTEN UP!"

I jumped at how loud her voice was, and she smiled, pleased with the effect, as everyone instantly stopped talking and focused their full attention on her.

"This, as I'm sure most of you know, is Cassandra. She has had prior duelling experience, and like us, is often the target of the Carrows' ire. From now on, she will be teaching us duelling and defensive spells."

There was a lot of murmuring in the crowd. Then someone spoke up. "But she's a Slytherin. How do you know she's trustworthy."

Neville smiled. "If she wasn't, she wouldn't be here. I've changed the Room of Requirement a little busy telling it to only allow members of the DA and those who mean the DA well to enter. Anyone else during this time that we are occupying the DA room will be transported into a broom closet, or wherever else they want to go, but not here."

There was silence for a moment.

"What will you be teaching us?" said someone else from the crowd.

"Expecto patronum," I said aloud, allowing my heart to fill with passion and power, and instantly my patronus took corporeal form, and I turned from my familiar wolf to face them. "I've heard that many of you can perform the patronus charm. But how many of you can send messages using the patronus?"

There was silence in the crowd.

"It's very simple. Just a swish of your wand and the words "nuntio expecto" But it's less about the wand movement, and more about the intention. Focus on your intention to send a message to a select someone, and let your intentions fill the entire patronus. Now pair up, and don't forget - nuntio expecto. Your intentions will make or break the patronus."

I watched them break into pairs, facing one another. To my surprise, there were some who seemed to continue having trouble forming a patronus, so I walked over, swallowing my unease and discomfort stemming from unfamiliarity and uncharacteristic shyness.

"Don't just focus on a happy feeling. Sometimes it's not enough. Focus on your intentions - to protect, to survive. Focus on any powerful emotion you have - ambition, passion, anger, anything that makes you feel strongly about, say, being against the Dark Lord. But it has to be empowering, hopeful. Then say the words, expecto patronum."

I was a little hurt when that person turned around to glare a little, but he seemed in the end to decide to take my advice, and instantly a silvery shape was formed, almost turning corporeal, but not quite. "Try again," I said, before moving on.

Those who similarly were still unable to cast a patronus, I grouped them together to focus on that. When they were finally able - the three quarters who could - I instructed them to try the message sending. Then I gathered all of those who seemed capable of producing a patronus and succeeding in sending the message, and told them to focus on not allowing anyone to hear the message but the one. Then I let them try again in pairs.

Luna and Ginny were practising together, and I couldn't help but be impressed when on Ginny's first try, the horse ran straight down to Luna, and I could see it giving a message that I could not hear. "Well done," I told her. "It's impressive."

Ginny looked at me sourly, then sighed. "I wish you were an imbecile, but you're actually quite good at this."

I nodded. "I had good teachers. Nothing more. You have talent, though. Are all your Hogwarts defence teachers like Amycus?"

Ginny groaned. "Not all. Amycus is one of the better ones because he at least gives advice on how to do the dark arts right. The rest...I never learned a single thing from the other three defence teachers, and even a more capable one was too busy making snide comments and being biased to actually teach properly."

I winced in sympathy. "Well, keep practicing."

I moved over to the other group, where I noticed Neville was still struggling with producing a full patronus.

"Is it really necessary to have a corporeal patronus to send a message?" he asked.

I looked at him contemplatively, then conjured my own patronus, forcing it to remain mist-like and silvery. Then, nonverbally, I informed the patronus of my message to Neville.

To my approval, my silvery shimmery mist headed instantly in Neville's direction, and his eyes widened as he listened to my message. Then he looked at me. "Teach me," he insisted.

I inclined my head. "It's usually easier when the patronus has a shape, because the patronus is created with emotion and moves with intent. Only when you are secure in your personality and know yourself very well can you pass on your message. I would still recommend you learn how to do a proper patronus, but I suppose it's no harm your trying to doing it in a non-corporeal form. Cast your patronus."

Neville did as I asked.

"Now focus your intent on sending me a message. And say the incantation. Nuntio expecto."

"Nuntio expecto," he informed the shimmering blob. Then he recited his message.

The shimmery mist came for me, but died along the way.

Neville deflated.

"Maybe your emotions are not strong enough. Tell me, what matters to you most in the world?"

Neville hesitated. "Making my parents proud."

He looked uncomfortable sharing, and before he could convince himself it was a bad idea, I interjected: "Good. Then focus on making your parents proud. Feel that drive to impress your parents, and channel it into the patronus charm. Then say it. You don't need to yell it."

Neville, who was indeed taking a deep breath to do just that, winced. His voice that came out was flat, nothing near as thunderous and commanding as it had been on his earlier attempts that I had noticed. Instantly, however, the silver-blue mist did finally take form into a large dog with a flattish head.

"A St. Bernard," I said, nodding. "Impressive. You must very loyal."

Neville flushed. "You can tell a person's character from their patronus?"

I nodded. "Not character per se, just a little about who they are, deep inside. It doesn't represent your outward personality but something necessary and essential within you. For example, I'm unsurprised Ginny has a horse patronus. She is independent, bold, and stands up for her beliefs. Luna is unusual, eccentric, but well-meaning, kind hearted. You have no doubt heard the Wizarding tales of the march hare. Fair warning, if I were you, I would be wary of Seamus Finnigan. Of his personality, at least. He is bold and brash on the outside, but foxes are cautious, cunning. He's hiding an essential part of himself. And Anthony Goldstein's favourite animal, I hear, is a goldfinch. His patronus is a goldfinch. Always be cautious of people who hide themselves or understand themselves overly well. They are not people to be crossed."

Neville looked conflicted. "And you? What does your patronus say?"

I conjured up the wolf, barely even thinking about it, and he came, his bluish-silver eyes glowing in a thick halo of light. "Like you, I'm loyal," I answered. Just then, my watch chimed, and I knew it was time. Tapping the watch lightly with my wand, I extinguished the wolf and walked back to the centre of the room.

"Everyone, good work today. Now you guys can communicate without anyone overhearing you. Keep practicing, and next week we can get started on actual duelling," I said.

The students strolled out of class, even as I mused, privately, about something I had read. As they left, I was surprised that the boy I had provided my first ever official defence advice to actually came up to me and said: "You're not half bad at this, for a Slytherin."

I snorted. "Yeah? Well, you catch on quick, for a Gryffindor."

He laughed too, and stretched out a hand. "Ritchie Coote. And that's Demelza Robins." He pointed at another girl who was behind me, grinning. "Thanks for your advice. I've never been able to do a full patronus before."

I shook my head. "It's nothing," I said. "Just my job."

"Well, you're good at this job, so stop being modest," came a new voice, one that was flat and unwillingly impressed. Ginny stood next to Demelza, her arms folded across her chest. "I would almost have thought you had been doing this for years if it weren't for how your arms were shaking the entire time."

I glanced down at my arm. It was still shaking, but I laughed anyway and nodded. "Maybe it'll stop shaking if you'd invite me back, except I don't even know when the next time D.A. meets. I'm assuming it's not same time next Thursday."

Luna hummed. Her wand swished, a round gold coin appeared. My eyes widened as I took it from the air, and studied it, seeing the numbers being exactly the date of that day.

"Protean charm," I said. "Will I be getting a coin like this?"

Neville hesitated. "Well, we haven't managed to find gold coins to cast it on, and it's very advanced magic. We haven't found a way to do it."

I looked at them carefully, before flipping out the little bit of alchemical gold I always carried on me, which I quickly changed into a round coin shape. "Do you mind?"

The three of them shook their heads. So I quickly casted the protean charm, replicating the same design onto my own coin, which I slipped into my pocket, and returned the other to Luna.

"Keep checking it. It should burn hot when I change my coin to reflect the new date and time," Neville advised. I nodded, and overheard Ginny saying: "Quidditch practice tomorrow, five in the afternoon. Tell the rest."

Demelza and Ritchie both nodded and left the Room of Requirement.

"Well, we should get going as well," Neville said. "See you around?"

I nodded, not sure if I was a little upset they didn't invite me along with them, but it suited my needs. I walked out of the room after giving them a three minute head start, then turned back around, paced three times, and entered the Room of Requirement.

That must be the place where lost things went. There was a large black cupboard, a tiara on a marble bust, birdcages, spare books that seemed to shiver and twitter, all sorts of odd things that I was not sure was even safe to touch. Then, at the very end, propped against the wall next to a frosted glass window, a tall ornate mirror stood, with clawed foot and a heavy gold frame. The gilded words "Erised stra ehru oyt ube cafru oyt on wohsi" was written at the top.

"I show not your face but your heart's desire," I murmured, well familiar with this particular relic, one of the finest alchemical creations.

Then I stepped right in front, and froze at the image before me.

I was surrounded by my old Durmstrang friends, and also by my new Hogwarts friends, and in the background, the pack of pale, ghostly wolves dwelled, their smoky green eyes and white arctic fur glowing in the dark. I pressed my fingers against the cold mirror, feeling it heat beneath me, and felt a sudden sorrow seep into my heart.

I had already anticipated that.

Sitting down heavily, I wondered about the lodestone used to make up the mirror, and how it's creator had managed to piece it together to make such a unique mirror.

When I arrived at dinner, just in time to watch all the food disappear, the rest of my friends glared at me. "Where in Merlin's name were you?" Millicent demanded.

I forced a sheepish smile. "Fell asleep in a classroom, right on top of my Charms work this time. I think I've got a bit of ink on my cheek."

The rest shook their heads. They had caught me snoring over my Transfigurations work only the previous week, so my excuse was not completely out of the possibility. Yet as we stood to head back to our common room, I could not feel more alone than I did in that instant.