"So, this is the cave," Isaac said, not quite a question.
He stood with his hands in his coat pockets, hazel eyes moving across the cliff face with the quality of attention that Sirius had learned, after years of working alongside him, meant he was calculating things he wasn't saying yet. The sea wind off the North Sea pulled at his hair and he ignored it with the practiced indifference of a man who had stood in worse places in worse weather and had developed opinions about which discomforts were worth acknowledging.
"This is the cave," Sirius confirmed.
Isaac was quiet for a moment. "Six hundred Inferi," he said. "In there?"
"Approximately."
"Approximately," Isaac repeated, with the tone of a man deciding how he felt about that word in this context.
When Sirius asked Kracher to send him to the cave, he had gone alone at first. Not because he was being heroic. Far from it. You don't just go into the cave full of Inferi by yourself. Of course, given how Kreacher described it, there was more than enough Inferi in the cave to overwhelm one wizard especially since Regulus was already in a poor state before he was grabbed into the water.
But Sirius still needs to know. He needed to know with his own eyes. That Regulus is not dead and how much of a threat the Inferi are in the cave before considering a rescue.
In the past, Sirius wouldn't care and would probably barge in there, but Sirius isn't the rebellious and impulsive teen anymore. He was a seasoned veteran and has now a family to think of. Not to mention he already knows the risks of recklessness. Recklessness means death not just to you but everyone you dragged with you.
So, he didn't think it was also a good idea to seek out help to rescue his brother if his brother isn't viable anymore. His hair raised when he entered the cave. That's just how it is with Inferi. They were mindless and difficult to kill. Fire spells work on them but it requires a large amount of constant stream and even when you are dealing with one Inferi, another will pop up behind you. Protego doesn't work on them since Inferi attacks are physical not magical.
So, when Sirius sought out a life signature, he managed to confirm it. In the middle of the lake was a faint signature that Sirius recognized. His brother is alive. But his eyes filled with horror when his Revelio showed what surrounded his brother. It was a horde of Inferi.
"Merlin's balls." Sirius cursed.
It was large enough to fill an army! Sirius has fought Inferi before. They were a popular staple among dark wizards. He could proudly say he can take on ten and probably twenty on a good day. But six hundred? That is a suicide mission. Sirius could not rescue his brother alone!
This is why he reached out to the Custodians, more specifically Isaac Thornwick. His recruiter, handler and now boss and they mobilized as soon as possible. Not because they need to rescue Regulus fast but because they are highly concerned about a horde of this amount existing.
"Captain!"
"Major!"
The others called out.
Sirius turned to the men and women who had arrived at the entrance. Sixteen of them, counting himself and Isaac — though raid was probably too formal a word for something the ICW hadn't sanctioned and the British Ministry of Magic didn't know about. Not that the Ministry had ever been particularly attentive to such things. Sirius knew that better than most.
"Captain! Is it true?" Chinedu Okoro came marching toward him, large enough that the sea wind barely registered against him, his voice carrying the way it always did — which was to say, clearly audible from the next county over. His eyes were suspiciously bright. "Are you really resigning?"
Sirius sighed. "Yes, Edu."
"NOOOOO!!!! Why?!"
"Oh, please." Beatriz Cavalcante crossed her arms, dark hair pinned back with the efficiency of someone who had long since stopped having patience for dramatics. "He has four children and a wife, Edu. He has to settle down at some point."
"I'll say. Captain's wife is a total babe—OWWWWW!"
The sound of a palm connecting with the back of Lucas Belrose's head was sharp enough to cut through the wind.
Sirius didn't need to turn around. "Thank you, Mara."
Mara Volkov said nothing. She rarely did.
His gaze drifted to the edge of the group, where four figures stood slightly apart from the Custodians. They hadn't announced themselves when they arrived. They didn't need to.
They are combat healers. Esme's people.
He had tried to talk her out of sending them. Not because he doubted them, but because accepting them meant accepting that she was right to worry, and he had wanted, just this once, not to give her reason to. She had looked at him with the expression she reserved for arguments she had already won and hadn't yet bothered to say so, and he had stopped arguing.
The tallest of the four caught his eye and gave a small, precise nod. It was the kind of nod Esme gave when she wanted him to know she was paying attention. Sirius held it a beat longer than necessary, then looked away.
"Alright, that's enough."
Isaac didn't raise his voice. He never needed to. There was a quality to the word that landed like a hand on a shoulder. It was firm, final, no discussion required. The group settled almost immediately, Edu's residual sniffling notwithstanding.
"Before we go in," Isaac said, "there are a few things we need to establish." He turned to face the cave entrance, hands still in his coat pockets, and spoke the way he always spoke in a briefing. "Sirius has confirmed a life signature at the center of the lake. That's our objective. Everything else is secondary."
He turned back.
"The Inferi respond to fire. So, everyone be gearing up with fire magic. That's our primary tool inside. However —" he paused, and the pause had weight, "— we are working in an enclosed space. Uncontrolled fire means oxygen depletion. We are not here to cremate six hundred Inferi. We are here to hold a corridor long enough for Sirius to cross the lake and come back out. Controlled, directional fire. Push them back toward the water or seal them inside for good. Nothing more."
"Bubble-head charms," said a voice from the back. Mara, already casting hers with the brisk efficiency of someone ticking items off a list.
"Before the potions," Isaac confirmed, nodding at her. "Charms first. Then potions. In that order."
On cue, the healers started moving with vials that everyone recognized as fire resistance potions. Those would be helpful to keep themselves from fire related injuries as fire is very unpredictable.
One of the healers, Bastien Lefebvre, stepped forward from the edge of the group, a worn leather satchel over one shoulder and a crate of small glass vials tucked under his arm. He was younger than most people expected healers to be, with the careful, slightly earnest manner of someone who had learned his profession in places that didn't allow for mistakes. He set the crate down and began distributing the vials with quiet efficiency, not quite meeting anyone's eyes.
"Three each," he said, in careful English with a French accent that thickened slightly when he was concentrating. "They will last one hour. Do not take the second until the first has worn off or you will —" he paused, searching for the word, "— overwhelm the system."
"These are Esme's?" Sirius asked, turning one of the small vials over in his fingers. The liquid inside was a deep, steady amber, nothing like the watered-down fire-resistance draughts he had used in the field before.
Bastien nodded. "She brewed them herself. All of them." A small, genuine smile crossed his face. "She started the moment she called us."
Sirius looked at the vial for a moment longer than necessary.
Of course she had.
"Excuse me."
Bastien turned. Wyatt Vance was leaning against the cliff face with his arms crossed and his cowboy hat tilted at an angle that suggested it had been tilted at that angle deliberately, which it had. He had the quality of stillness that men from very flat, very open places sometimes developed. Unhurried, grounded, and entirely comfortable taking up space.
"I just wanted to say," Wyatt said, with a slow smile that had apparently not received the memo about the six hundred Inferi fifty feet away, "that is a very impressive satchel, darlin."
Bastien blinked.
"The — the satchel?"
"Mm." Wyatt nodded seriously. "Very well-organized. I can tell a lot about a person from how they organize their satchel."
Bastien looked down at his satchel. Then back up. His ears had gone slightly pink. "I — merci. Thank you. It is just — it is practical—"
"Very practical," Wyatt agreed, still with the smile, still leaning, showing absolutely no signs of moving on.
"Wyatt." Bea didn't look up from checking her wand. "Do you ever stop flirting?"
"Not historically, no," Wyatt said pleasantly while keeping his eyes at Bastien.
Bastien had found something extremely interesting to look at on the label of the nearest potion vial. The tips of his ears were now definitively red.
"Right." Isaac's voice cut through the moment. He had the expression of a man who had long since made his peace with the people he worked with and had chosen to focus on the things he could control.
"Formation. Sirius — you're crossing alone. The moment you're on the water, the rest of us establish the fire line here —" he indicated a point just inside the cave entrance with a gesture that managed to convey an entire tactical map, "— and we hold it. The healers' position at the entrance. If something comes through the line, you deal with it and you call it out. No heroics, no freelancing." His eyes moved around the group and landed, briefly but meaningfully, on Edu.
Edu straightened up. "I am the picture of restraint."
"You are many things," Isaac said. "Three hours. That's our window. After three hours the potions are gone, and the oxygen situation becomes a conversation I don't want to have." He looked at Sirius. "Questions?"
Sirius looked at the cave entrance. At the dark beyond it, the smell of cold water and something older underneath. Somewhere in there, past six hundred things that had once been people and were no longer, his brother was breathing.
Still breathing. After all these years.
"No questions," he said.
Isaac nodded once. "Then let's go."
*****
The cave swallowed sound.
That was the first thing Sirius noticed when they crossed the threshold. Not the cold, not the dark, not even the smell of standing water and something older underneath. It was the way the cave took the noise of the sea and closed a door on it. One step inside and the world outside ceased to exist. There was only the drip of water, the low hiss of their lit wands, and somewhere in the dark ahead, the surface of the lake moving with things that did not breathe.
The white whisps were already there.
Sirius saw them the moment his eyes adjusted — thin, drifting threads of light that moved against no current, tracing the cave walls like something written in a language he almost recognized. They weren't responding to the Custodians' wands. They weren't responding to anything. They simply existed, patient and faintly luminous, the way embers exist long after the fire has gone.
He had seen residue like this once before, in the lower vaults of Gringotts, before everything changed.
He kept moving.
"Formation," Isaac said quietly, and the team spread without further instruction, the ease of people who had done this in worse places. The fire line established itself in a rough corridor between the entrance and the water's edge. Six wands, controlled flame, low and directional the way Isaac had briefed. Not enough to consume the air. Enough to hold a gap.
The Inferi hadn't moved yet.
They were there. Sirius could feel them but they hadn't moved. The firelight caught edges. The white of a hand. The pale suggestion of a face.
"They're waiting," Edu murmured, and for once his voice was very quiet.
"They're not waiting," Isaac said. "They don't wait. Move."
Sirius moved.
The boat was where Kreacher had described it, pulled up against a narrow outcropping of rock at the water's edge. Small. Old. The kind of vessel that looked like it would take one person and resent even that. He lowered himself in carefully, Regulus's absence a strange weight he was already carrying, and pushed off from the rock.
The lake was black and still.
He didn't look over the side.
Behind him, the fire line held. He could hear it. The steady, controlled burn, the occasional sharp crack of a spell redirected, Isaac's voice in short precise increments calling adjustments. The Custodians were good. He had always known they were good. He was trusting that goodness now with something he couldn't afford to lose.
He poled the boat forward with his wand arm, his eyes on the center of the lake, and ran a locator charm low and quiet.
The signature came back immediately.
There. Twenty feet ahead. Faint as a candle behind glass but there, unmistakably there, the frequency of it something Sirius had not felt in so long he hadn't been certain he still remembered what it felt like.
He did.
He found Regulus on a flat shelf of rock just beneath the surface, half-submerged, one hand curled loosely at his side as though he had simply lain down and closed his eyes. He looked like in Sirius's mind stalled on it for a moment. He looked like one of them. The pallor of him. The stillness. If not for the signature still pulsing faintly in his chest, Sirius might not have known the difference.
He reached down quietly and took hold of his brother's arm.
"Reg," he said. Not loudly. Not the way he had imagined saying it in the abstract, in the months since the entity had told him his brother was alive. Just the word, quiet, like resuming a conversation that had been interrupted.
He pulled him up.
Regulus was soaking wet and burning with fever and he weighed almost nothing, which was its own horror. His frame so reduced that Sirius kept adjusting his grip in disbelief. He already looked like one of them. He had been fighting that resemblance for five years with nothing but sheer stubborn magic, and the magic was almost gone.
"I've got you," Sirius said.
Regulus made a sound. Not a word, but more like an exhale.
Sirius tightened his grip and started back.
Even with that, the noise was too much.
*****
The fire wall on the left flank went out.
It snuffed like a candle, and in the sudden dark the Inferi came through the gap like water through a broken dam. Their screeches echoing sharply in the dark.
"Left flank is gone!" Mara's voice, stripped of everything but the information.
Sirius heard her but couldn't turn. He had Regulus, and that was the entire problem. He had one arm locked under his brother's knees and one around his back and his wand hand was occupied and the Inferi were coming.
He moved. Three steps toward the shore, the water dragging at his boots, the cold of it so absolute it had stopped feeling like cold and started feeling like absence. Two more steps. Regulus exhaled again against his shoulder.
"I've got you," Sirius said again. He wasn't sure Regulus could hear it. He kept saying it anyway.
"Sirius, move!" Isaac, from somewhere to his right, his voice carrying the specific quality it got when he was calculating whether a situation was recoverable.
The path to the shore was closing.
The Custodians were holding — barely holding, six of them maintaining fire lines that had been designed for a corridor and were now being asked to cover a breach. The flames were lower than they had been, magical output flagging after twenty minutes of sustained casting in a cave that seemed to eat light. The Inferi pressed against the fire with the mindless, remorseless patience of things that did not experience pain or exhaustion or the concept of a tactical retreat.
Then they came from the ground.
That was the thing about Inferi that no briefing ever quite prepared you for. It isn't the numbers, the cold, nor the faces you should worry about. It was the ground. The moment you thought you thought you eliminate the threat, more of them will keep springing out the ground, and suddenly the corridor that had been holdable was not holdable anymore.
"Ground!" Bea's voice, sharp with warning.
Three of them erupted between Sirius and the shore.
He couldn't cast. He couldn't put Regulus down. He couldn't go back.
"Fuck." Sirius hissed when he saw ten barreling towards him.
"Confringo!" Sirius casts and one of them was hurled away but it immediately stood up and came running at him fire and all. "Incendio! Expulso! Incedio Maxima!"
He can't go on like this.
At this rate, he will run out of energy.
The whisps moved.
He noticed it the way you notice something in peripheral vision. The drifting threads of light along the cave walls had stopped their aimless movement. They were orienting. Toward him. Toward the point where he stood in the shallows with his brother in his arms and three Inferi between him and the shore and no hand free to stop them.
The air changed.
It was subtle at first. It felt heavy like a pressure that sat behind his sternum rather than against his skin. The sound changed with it. The shrieks of the Inferi, the crack of spells, Isaac's voice calling adjustments — all of it blurred at the edges, softened, the way sound softens when something louder is coming.
Sirius did not decide anything.
That was the thing he would try to explain later and never quite manage. There was no decision. There was Regulus in his arms, and the Inferi closing in, and the whisps converging, and then there was something moving through him that had no name he knew yet. It was vast and unhurried and extremely certain, the way the tide is certain, the way the pull of the earth is certain, and his body responded to it before his mind caught up.
The hum began in his chest.
Not a spell. Not an incantation. Something older than either, something that wanted to be sound the way the first sounds had wanted to be sound, rising through him without asking permission. The cave walls vibrated with it. The water surface trembled.
The whisps blazed white.
And then the hound came.
It did not arrive from anywhere. It was simply suddenly present — enormous, spectral, the shape of it assembled from something between light and intention. Fire breathed from its fanged mouth and burned in its eyes, not the orange red of ordinary flame but white, the same white as the whisps, ancient and absolute.
The Inferi saw it.
That was the thing that would stay with Sirius long after — the fact that the Inferi reacted. Things without minds, without fear, without any surviving instinct beyond the single directive to grab and pull and drag under — and they recoiled.
The ones nearest the hound lurched backward, their screeching pitching upward into something that didn't sound like a threat anymore. It sounded like recognition. Like something in whatever remained of them knew what was standing in that cave and understood, in whatever way dead things understand anything, that it outranked them entirely.
The hound moved.
It didn't run. It didn't lunge. It simply advanced, unhurried, the way something moves when it has never once in its existence needed to hurry, and where it passed the Inferi came apart. Not burning. The bodies dissolved from the ground up, flesh running like wax, the screeching cutting off mid-note as each one went, until the only sound left was the hiss of them meeting the cave floor and the drip of water in the sudden quiet. The ones still clawing up through the ground stopped. Hands that had broken the surface simply stilled, half-emerged, and then receded, drawn back down into the rock as though the earth itself had reconsidered.
The cave went quiet.
The hound stood at the water's edge for one moment longer, its white eyes finding Sirius in the shallows with something that was not sight exactly but was not nothing either. Then it was gone.
Sirius was on his knees in the shallows. He didn't remember going down. Regulus was still in his arms but the strength had gone out of him so completely that kneeling was the best available option. The hum was gone. The heaviness was lifting. The whisps had dimmed back to their ambient drift as though nothing had happened.
The hound was gone.
"Sirius."
Isaac's voice, from very close. Then someone held him up.
Sirius looked up.
The Custodians were standing in the sudden silence of the cave with the expressions of people who had seen a great many things in their careers and were currently recalibrating. Edu's mouth was open. Bea had her wand still raised and appeared to have forgotten about it. Even Mara looked — not shaken, but recalibrated, her eyes moving between Sirius and the space where the hound had been with the expression of someone updating a file.
"That," Wyatt said, from somewhere at the back, in a voice that had lost most of its drawl, "was not in the briefing."
Sirius looked down at Regulus.
Still breathing. Shallow and rattling and fever-hot, but breathing. His face slack with the profound unconsciousness of someone who had been holding on by will alone and had finally, with permission, let go.
"Let's get him out," Sirius said. His voice came out steadier than he had any right to expect.
Isaac looked at him for a moment. Then he nodded once, and reached down, and helped Sirius to his feet.