The days stretched longer and longer as May drew to its close. The sun was already high in the sky when the owls arrived at the breakfast table to deliver the post on the last day of the month, one of them landing on the Hufflepuff table with a small, peculiar shaped parcel attached to its leg, which it stretched out to Artemis.

Artemis took the parcel from the bird, and opened the parcel to reveal a silver key, decorated with green-painted leaf-like tendrils that rolled down the length of the handle.

"What's that?" asked Tonks, and both she and Penny frowned at the item over the top of their Potions revision.

"It's a key," said Artemis, smiling as she read the handwritten note her great-uncle had wrapped into the parcel containing the key. "Sickleworth had it this whole time."

"What does it unlock?"

"Well, judging by the fact that it's decorated with Gillyweed," Chiara looked closely at the key, "I'd assume that it unlocks something to do with water."

"The Vault in the lake, maybe?"

"That's what I'm hoping." Artemis nodded. "I'll see what Bill makes of it."

As breakfast finished, Artemis placed the key in her pocket and loitered near the top table of the Great Hall, where Bill was mid-conversation with Hagrid the gameskeeper. When the two had finished talking and Bill left the table, she rushed to meet him.

"What do you think of this?" she asked him, holding the key out for him to inspect. Bill sighed heavily.

"Good morning, Bill, did you sleep well? Yes, I did. Thank you for asking," he said, but he took the key from her. "What does this do?"

"I was hoping you might tell me. Rakepick sent me and Sickleworth into Filch's office to find it back in my fourth year. She said it was important, and so I thought it might-"

"Be needed to open the final Vault? It would make sense, what with the Gillyweed."

"That's what Chiara said," Artemis frowned. "I didn't know what Gillyweed has to do with the lake-"

"It makes you breathe underwater."

"- but Duncan said that Olivia Green found a key that she thought would open the final Vault, and it reminded me of this one."

"Nicely remembered," said Bill. He lowered his voice slightly. "You know, we might need this pretty soon."

Artemis tilted her head to one side. "What do you mean?"

"Hagrid was just telling me that the Grindylows have started acting aggressively, same as they did last year. If you ask me, it won't be long until..."

"The statue curse gets released," Artemis finished Bill's sentence for him, and he inclined his head, his face grim. Artemis looked at the key. "We need to get to that Vault. Tonight."

"Tonight? Artemis, that's... We aren't ready, we don't even know-"

"That's the problem, Bill! No one knows how to open this Vault, not for certain."

"No, but if we take a bit longer to research, then we can have a better idea of what we're doing."

"If we take much longer, more people will get cursed, or the Cabal might beat us to it," Artemis argued. "We can't risk losing out to them now just so we can spend longer reading books for clues that might not even be there. You know, the clues might even be hidden inside the Vault itself!"

Bill exhaled, his features softening as he did. "Okay, you have a point," he told her. "A good point. But I'm just as worried about the Cabal as the Vault. Who knows what they know already? You said they have an informant in the Auror office."

"They did have one, but not anymore. Kingsley said they caught him. Someone called Williamson, I think."

"And did Williamson tell them anything about R after they caught him?"

"Nothing yet. Apparently he's still pretending to know nothing about it all, even though Moody told him the information that got leaked and no one else. But at least the Aurors are all trustworthy now." Artemis shrugged. An idea stuck her, and she turned to Bill. "What if we ask the Aurors to guard the school while we go down to the final Vault? That way, we won't have to worry about the Cabal showing up, because the Aurors can stop them getting as far as the lake."

"That's not a bad idea," said Bill, nodding slowly. "How long will it take for you to arrange that with Kingsley?"

"A day, maybe?" Artemis said. "Could be less. We might even be able to get to the Vault tonight." Bill rolled his eyes. "What?"

"You really haven't changed a bit, have you?"

***

Bill might have been sceptical about Artemis' desire for haste, but both Kingsley and Mad-Eye Moody had thought her idea of getting to the Vault as quickly as possible a good one. The following night, an Auror patrol was set up around the perimeter of the school grounds, and the Circle of Khanna met in the entrance hall of the castle. The doors were open as they gathered, giving them a clear view of the courtyard beyond, illuminated by the crescent moon.

"That's everyone," Bill told Artemis, his eyes scanning the group as if he were counting them. Artemis nodded.

"Good. That's good," she said. "Right, so this is it. The final Vault." Jae wolf-whistled quietly, and Artemis rolled her eyes before continuing, "The Vault is in a cave in the middle of the lake, and we are going to need to swim there. That means you'll need this."

She nodded to Tonks and Tulip, who began to hand out clumps of a stringy green plant to the others.

"This is Gillyweed, Tonks and I nicked it from the greenhouses. It'll let you breathe underwater."

"What happened to the Bubblehead Charm we used last year?" asked Barnaby, holding up a piece of Gillyweed and sniffing it suspiciously.

"Nothing happened to it, it's just that we might need to keep our wands free, that's all. The Cabal might be there, we need to be ready to defend ourselves if necessary."

Penny's blue eyes widened. "I thought you said the Aurors would be here to deal with the Cabal."

"Yeah, they will. They're all stationed around the edges of the grounds keeping watch, and they have signals and stuff set up in place if there's any trouble. But Moody still said we need to keep our wits about us, just in case."

Tonks screwed up her face and one of her eyes doubled in size, its iris changing colour to a bright electric blue.

"Constant vigilance!" she said in a gruff voice that was impressively similar to that of Mad-Eye Moody. A few of the others laughed, but most did not.

"I know it might be dangerous," Artemis told them. "It's okay if you've changed your minds. It's not too late to turn back."

"Like hell it isn't," muttered Merula. "Come on, let's do this."

Bill and Artemis led the Circle of Khanna out of the main doors of the castle into the darkened entrance courtyard, on the other side of which a set of steps carved into the cliffside wound down to the lakeshore below. As they walked across the courtyard, wands raised and ready, Artemis felt a hand on her right shoulder. She turned to see Charlie Weasley behind her, staring at the cloisters with his eyebrows knitted together.

"We weren't expecting anyone else, were we?" he asked, his voice low.

Artemis shook her head and followed his gaze to see that someone was standing in the cloisters, tall and cloaked in shadow. As they stepped out, the moonlight illuminated their features, their height cheekbones and silver-streaked dark hair. It took a moment for Artemis to realise that she recognised the newcomer.

She wasn't the only one.

"Dad?" Tulip pushed past Artemis and Bill to approach the wizard in the cloisters. "What are you doing here?"

"Shacklebolt told me what your friends had planned," said Ambassador Karasu, with a dirty look in Artemis' direction. "I came here to make sure that you have nothing to do with this."

"But-"

"I don't know why Shacklebolt even agreed to this nonsense. This is not something for teenagers to be engaged in, let alone when one of those teenagers is my daughter."

"We know what we're doing, Dad," Tulip rolled her eyes.

"This is far too dangerous for you. I forbid you to have any part in it."

"I'm of age. You can't forbid me to do anything."

Tulip's words seemed to have hit a nerve with her father. He reached out and grabbed her by the arm, so fast and so forcefully that Artemis was certain his hand would leave a mark.

"Let go of me!"

But Karasu did not let go of Tulip. Instead, he tightened his grip. Tulip winced as she tried to wriggle free, to no avail, and Artemis raised her wand, ready to take matters into her own hands. Before she had the chance to do anything, however, Barnaby Lee had already pointed his wand at the ambassador, his jaw clenched and shoulders shaking.

"Relashio!"

A flurry of purple sparks issued from Barnaby's wand and hit Karasu in the wrist. His hand jerked as if it were going into spasm, and his grip on his daughter's arm loosened. Tulip wrenched her arm away from him and rejoined her friends.

"My friends are going to the lake, and they are going to break these curses once and for all," she told her father in a voice that was laced with fury. "I am going with them, and there is nothing you can say or do to stop me, or any of us, for that matter."

As she spoke, Tulip's almond-shaped eyes were narrowed and fixed on her father, but he no longer seemed to be looking at her. Instead, his gaze had settled on the far corner of the courtyard, at the top of the cliffside steps. Frowning, Artemis turned to see what he was looking at, and her stomach lurched.

At the top of the steps were two more people: a pot-bellied wizard with a darkened nose who Artemis immedaitely recognised as her former teacher, Professor Topsy, and a tall, grey-haired witch in purple robes who she didn't recognise, but knew without asking who she must be. If her violet-coloured eyes hadn't given her away, the fact that Merula Snyde had tensed beside her was all the proof she needed. This had to be Madam Buckthorn, Merula's aunt, the head Healer of St Mungo's Hospital, and the Director of the Cabal.

"You tried, Karasu. Looks like your daughter is just as disobedient as my niece. You know, my dear, you should listen to your father," said Madam Buckthorn, smiling passively at Tulip. "He's right, this isn't a matter for teenagers. It's very good of you all to have helped Miss Hexley with the last few Vaults, but I must insist that we take it from here." Her eyes settled on Artemis briefly, before she turned to talk to someone behind her. "I see what you mean. She really does look like her brother. I do hope that she will not cause us as much trouble."

Artemis glared at Madam Buckthorn. "Don't you dare talk about my brother," she said, raising her wand. "If it weren't for you, he'd never have been in any trouble at all."

"Did you not learn anything from the prophecy you stole, Hexley? You and your brother have been in trouble since you were born."

"What do you... Wait. How do you know about us stealing the prophecy?"

There was a soft laugh from behind Madam Buckthorn, who stepped aside to reveal another witch, one with dark hair and glasses that caught the silver moonlight. Artemis' heart skipped a beat.

"Rowan?"

Of course, it wasn't Rowan. But the witch looked familiar, with her curly hair and bright green eyes. Artemis had seen her before, spoken to her, been helped by her.

Olivia Green.

"You? You're one of them?" Artemis frowned. "But you... You were Jacob's friend."

"I still am," said Olivia. "So is the Ronde. We all wanted the same thing. We're on the same side, Artemis."

"The Ronde tried to kill me. They did kill Rowan, Duncan... After everything that's happened, how can you be on their side?"

"The Final Vault requires a life," Olivia Green shook her head sadly, but there was no regret in her eyes. "Duncan and I both wanted to get into the Vaults with your brother. Duncan should have felt honoured to lay down his life for it. It wasn't his fault that his life wasn't the one that was needed."

Artemis looked at her in disgust. "Your friend died, and you don't even feel sorry about it."

"I feel sorry that his death was a waste. I should've known that he wasn't the one," Olivia's green eyes narrowed. "Oh, but your brother was always so very clever..."

Beside her, Madam Buckthorn let out a noise almost like a laugh. "He still is. It's a pity that he had to go and put himself in Azkaban prison so we couldn't have him lead us to the final Vault. Although, naturally, that's what he planned all along. We needed one of you to fulfil the prophecy, and without him, we'd have no choice but to have you do it. Which meant that we'd need you alive."

"Especially after our plan with Shiratori failed," muttered Karasu. "Damn that Kingsley Shacklebolt."

"Where is he?" asked Artemis, her heart sinking as she realised that if the Cabal was here, at the castle, then something must have happened to the Aurors who had planned to keep them safe. "Where is Kingsley?"

"I expect that Burke has led him and his team on somewhat of a wild ghost chase."

"Burke? The Metamorphmagus?"

"Loken infiltrated the Auror office almost a year ago, has been passing information ever since. You know that, though," Olivia said. "You told me about it, remember? That night you came to the Department of Mysteries." She shook her head. "I can't believe you trusted a stranger so easily, after 'everything that's happened'."

"Now, Olivia. We should be grateful that young Artemis was so generous in giving you that information. After all, if she had not, Burke would not have been able to frame another Auror and keep Shacklebolt's trust, which would have been a great shame. I always think it useful to have friends in high places." Madam Buckthorn nodded her head in Professor Topsy's direction. "Take Topsy for example. Or your old ally, Patricia Rakepick. Both of them were so good at making sure situations were taken care of..." She smiled as Artemis' hand tightened on the hilt of her wand. "Now, now, there's no need to fret. No harm will come to your friend Shacklebolt, or any of your friends here."

"I don't believe you," said Artemis, he feet shifting into a duelling position.

"You should. We aren't interested in harming others unnecessarily. The Vaults have had their life, so no more need be taken. You can thank Rakepick for that, Rakepick and your dear little friend. What was her name?"

Artemis narrowed her her eyes and pursed her lips tight together. She wouldn't allow these people to say Rowan's name. They didn't deserve it.

"Khanna," Topsy said, his words almost completely clear. "Rowan Khanna."

"Of course. Thanks to Rowan Khanna, the Vaults are yours to open, Miss Hexley. Now all you need do is lead us to them."

"I'm not leading you anywhere," Artemis growled.

"You don't have a choice," said Olivia Green. "Your brother made sure of that the moment he put himself in Azkaban, as did you, when you picked up that prophecy. You have to lead us."

"No, I don't," Artemis raised her chin and stared defiantly at Olivia. "The prophecy says I have to lead a circle. I already have one, right here. I don't need you, and I don't want you."

"Ah," said Madam Buckthorn. "That complicates things."

Artemis shrugged. "Not really. It's simple. I lead my friends to the Cursed Vault, we open it, and you lot bugger off. Pretty easy to understand."

"I do understand, Miss Hexley, but what you don't understand is that my previous comment about not needing to hurt any of your friends was based on the assumption that they would not get in our way. You will lead the Cabal to the Vault, and not your little friends, or there will be a conflict, which we will win."

"We'll see about that," said a voice - Merula's voice - from beside Artemis. She was staring at  her aunt with open revulsion, her hand trembling slightly as she gripped her wand with white knuckles. "Confringo!"

A jet of bright orange light burst out of Merula's wand and soared through the air in the direction of Madam Buckthorn. It looked like the curse might hit her, but she raised her hand and waved it once, deflecting the light before it could do any damage. But Merula had cast the first curse, and now more were following, as one by one, the CIrcle of Khanna turned their wands on the Cabal.

Battle had commenced. Tulip's father was duelling against the combined forces of his own daughter, Barnaby, Tonks, and Andre. Madam Buckthorn was up against Merula, Talbott, Ismelda, Jae, and Chiara. Topsy was fighting Ben, Liz, Diego, and Badeea; whilst Artemis joined Bill, Charlie, and Penny as they fought against Olivia Green.

The Circle of Khanna outnumbered the Ronde in terms of numbers, but each member of the Circle only had one wand, and just as Rakepick had known how to cast spells without one, so too did the rest of the Cabal. Despite seeming to have the advantage, the Circle found themselves having to fight tooth and nail to keep up  with the force of the spells the Cabal were throwing their way.

With Olivia not using a wand to cast her spells, Artemis was finding it hard to predict which spells her opponent would use, and at whom. It was making it harder to counter every move, and her companions did not have the advantage of her Legilimency.

As Artemis dodged a spell issued from Olivia's wand, Charlie pulled Penny out of the way of a sudden explosion caused by the snapping of Olivia's fingers. Olivia's lips curved into a smile that was more like a snarl, and she cast another curse with her wand in Charlie's direction.

Bill quickly cast a shield charm to protect his brother, exposing the side of his torso as he leapt to Charlie's defence. Olivia's free hand reached out and she clenched her fist, and Bill let out a cry of pain, his own hand reaching for his ribcage. Her nostrils flaring, Artemis volleyed her own curse in Olivia's direction, but Olivia pushed her hand forward, palm first, and the light from Artemis' wand stopped in mid-air and changed direction so that it shot straight back at her.

"Protego!"

A deep, rumbling shout echoed across the courtyard, and black wizard in deep purple robes entered the fray, his wand arching gracefully through the air, leaving a shield of silver behind it. Kingsley's shield charm hung in the air in front of Artemis, bursting into fractals as Artemis' returned curse hit it in the centre.

The Circle of Khanna's luck had changed; they had reinforcements. From the cliff steps, more Aurors were appearing: Moody, Scrimgeour, Proudfoot and Savage, and Dawlish, his arm no longer in a bandage. And from the castle, too, more adults were joining the scene: Professors McGonagall, Flitwick, Snape, and Sprout; Hagrid and Professor Kettleburn; and Madams Pomfrey and Hooch were all running out from the entrance hall.

The courtyard was no longer in shadow, instead it was alight with the flashes and beams of spells and curses as the Circle of Khanna, the teachers, and the Aurors combined forces to battle the Cabal.

Kingsley shot another spell in Olivia's direction before pulling Artemis into the cloisters.

"What took you so long?" Artemis asked him, and he shook his head.

"We were each watching an entrance of the castle," he told her. "A distress signal went up, so we followed the call, but it was a false alarm. When we saw the flashes from up here, we realised it wasn't a false alarm at all, but a distraction."

"That's because you never really caught the informant. It was Burke, the Metamorphmagus," Artemis said. "He's been in disguise as one of the Aurors all along. He's here."

Kingsley frowned and looked out of the cloisters at the battle that was still going strong in the courtyard. His eyes scanned the scene, before settling in the far corner.

"Dawlish," he muttered. "Of course."

Artemis looked out and saw that Kingley was right. Dawlish had disappeared from the scene, and in his place was a wizard with dark cropped hair and a sardonic looking expression, currently mid-duel with Tonks.

"What do you think he's done with the real-"

"I dread to think," said Kingsley, his eyes still on the scene. "Can they all do wandless magic?"

"Yeah."

"Then we'll need all the fighters we can spare."

"We've all been practising duelling. We can all stay and fight," said Artemis, but as the words came out of her mouth, she realised that they weren't true. "Except... Well, we still need to get to the Vault. That's why we're all here."

Kingsley frowned. "How many people do you need to take with you?"

"I'm not sure."

"In which case, Tiny, I want you to forget about this fight. You have your own to deal with. Run, take as many of your friends as you can without drawing too much attention to yourself, and get down to that lakeshore."

"But-"

"The rest of us can deal with the Cabal, you have to be the one to open the Cursed Vaults. Go. Run."

Artemis took a deep breath and wrapped her arms around Kingsley's waist before nodding her head and springing into action. She jumped out of the cloisters and weaved her way through the fighters, dodging and ducking and deflecting curses as she went, wondering how many of her friends she could pull away from the battle without either alerting the Cabal to their absence or giving them an advantage in the fight.

In the end, she managed to get eight members of the Circle of Khanna to follow her away from the courtyard and down the winding cliff path stairs: Bill, Penny, Tonks, Charlie, Ben, Merula, Barnaby, and Tulip.

"Where are we going?" Penny asked breathlessly, as Artemis led the group down towards the lakeshore.

"To the Vault," replied Artemis. "We have to get to that Vault and finish this. Now."

"What about the others?"

"Kingsley said more fighters were needed and that we couldn't draw too much attention to ourselves. This is the only way."

"But-"

"Hexley is right," Merula said. "We've come this far. We can't let them win. The Cabal or the Cursed Vaults."

They reached the bottom of the cliffs, and paused on the pebbled shore of the Black Lake. The atmosphere far quieter than it had been in the courtyard, though the noise of the fight could still be heard in the distance, and the night sky was still lit up with curses which from here looked almost like the fireworks that had been set off the night Jacob had left home, all those years ago. Artemis took a deep breath of the cool night air.

"They'll be okay," said Bill, smiling weakly at Artemis. "I taught them well last year."

Despite his comment actually reassuring her, Artemis rolled her eyes at him. She looked back at the lake. The surface of the water was completely still, as if no horrors lay in its depths. But they did, she knew that better than anyone.

Artemis reached into her pocket and pulled out a sprig of Gillyweed, and the others followed suit. Tonks made eye contact with her and grinned.

"Bottoms up, right?"