The coastal cliff face was even more forbidding in person than it had appeared in the memory. Jagged black rocks rose from a churning gray sea, waves crashing against them with violent force. The sky overhead was heavy with storm clouds, threatening imminent downpour. It was, Marquas thought wryly, exactly the sort of dramatic backdrop that would appeal to Voldemort's theatrical sensibilities.
Employing a Disillusionment Charm to blend with the rocky environment, he carefully made his way down the treacherous path toward where the cave entrance should be. The tide was higher than in Regulus's memory, making the approach even more dangerous.
"Couldn't have hidden it in a nice country garden," he grumbled, nearly slipping on the wet rocks. "Had to be the dramatic sea cave of doom."
After twenty tense minutes of careful climbing, he located the narrow crevice that served as the entrance. It was partially submerged now, requiring him to wade through chest-deep, frigid water to reach it. By the time he squeezed through the opening, Marquas was soaked and freezing, his warming charms struggling against the bone-deep chill.
"Excellent," he hissed through chattering teeth. "Just what every spy needs, pneumonia with a side of hypothermia. Very stealthy."
"Lumos Maxima," he intoned, his wand tip flaring with brilliant light that illuminated a vast cavern of smooth black stone. Unlike the rough exterior, this chamber showed signs of magical alteration, too perfectly formed to be natural.
At the far end, barely visible in the wandlight, was an archway inscribed with faintly glowing symbols. The entrance to the inner chamber, requiring a blood sacrifice to pass. Marquas approached cautiously, examining the runes without touching them.
"Typical dark wizard theatrics," he muttered, retrieving a small silver knife from his bag. "Nothing says 'evil lair' like demanding blood tribute. Would it kill them to install a doorbell?"
Rather than cutting his palm as Dumbledore had done in the books, an unnecessarily dramatic choice that would impair his wandwork, Marquas made a small, precise cut on his forearm, allowing several drops of blood to fall onto the stone archway.
The effect was immediate. The glowing symbols flared bright green, then faded as the solid rock of the archway dissolved into a misty opening. Beyond lay darkness and the unmistakable scent of stagnant water.
Marquas stepped through, his wand raised high, and found himself on the shore of a vast underground lake. The black water stretched into darkness, still as glass despite the churning sea outside. In the center of the lake was a small island, barely visible in the distance, with what appeared to be a faint greenish glow emanating from it.
But what immediately drew his attention were the signs of recent disturbance along the shoreline, footprints in the damp sand, a discarded robe, and most concerning, streaks of what looked like blood leading into the water.
"Regulus," he breathed, scanning the lake's surface for any sign of movement.
According to the books, the lake was filled with Inferi, reanimated corpses that would attack anyone who touched the water. But Regulus must have already triggered them if the blood trails were any indication. Which meant...
A splash from somewhere in the darkness made him freeze. Then another, closer. And another.
"Oh good, the welcoming committee is arriving. How thoughtful."
"Lumos Maxima Totalum," Marquas cast, channeling extra power into the spell. The entire cavern blazed with light, revealing a nightmarish scene.
Across the lake's surface, pale shapes were moving, dozens of them, corpse-white bodies with dead eyes and grasping hands, all converging toward a point about thirty yards from shore. In their midst, barely visible among the pressing bodies, was a dark-haired young man struggling desperately to keep his head above water while fending off his attackers.
Regulus Black was still alive, barely.
For a split second, Marquas hesitated. In the books, Dumbledore had used fire to repel the Inferi, specifically, a massive ring of enchanted flame that drove them back into the depths. But creating such a spell while simultaneously executing a water rescue would be nearly impossible, even for a wizard of his caliber.
He needed an alternative approach, and quickly.
Fortunately, Marquas had the advantage of both Snape's magical knowledge and his own modern problem-solving skills. He reached into his bag and withdrew two potions he'd grabbed specifically in case of encountering Inferi: Incendio Maxima Draught and a vial of his own creation that he called "Sunburst Solution."
Combining the two would be dangerous, potentially explosive, but desperate times called for desperate measures.
"Accio Regulus Black!" he shouted, directing his wand at the struggling figure in the water.
Nothing happened, as expected. Anti-summoning charms would be standard protection for a location this secure.
Plan B, then.
Marquas uncorked both vials and, with a practiced flick of his wand, levitated them high above the center of the lake where the highest concentration of Inferi surrounded Regulus.
"Confringo!" he cast sharply, targeting the hovering vials.
The explosion was spectacular. The combined potions detonated in a blinding flash of magical fire that spread outward like a miniature sun, illuminating every corner of the vast cavern. The Inferi nearest the blast were incinerated instantly, while those farther away shrieked and fled from the light, diving deep into the lake's black waters.
In the sudden open space created by the retreating Inferi, Marquas could now clearly see Regulus, pale, bloody, but definitely alive and struggling to stay afloat.
"Black!" he called. "Swim toward me! Now!"
Regulus's head turned weakly in his direction, recognition and confusion warring on his face. "S-Snape?" he gasped, choking on water.
"Less talking, more swimming!" Marquas snapped, maintaining a barrage of fire spells to keep the Inferi at bay. The initial blast was already fading, and the creatures would soon regroup.
With what appeared to be his last reserves of strength, Regulus struck out toward shore, his movements sluggish and uncoordinated. He made it perhaps ten yards before his head dipped below the surface, his strength clearly failing.
Damn it all, Marquas thought. There was no choice, he'd have to enter the water himself.
Quickly transfiguring his outer robe into a rope, he secured one end to a large rock formation and tied the other around his waist. Then, maintaining his wand aloft with a continuous stream of fire spells directed at the approaching Inferi, he waded into the freezing lake.
The moment he entered the water, he felt it, a bone-deep chill that went beyond physical cold, a sensation of dread and despair that clawed at his mind. The water itself seemed to resist him, becoming thicker, more viscous as he pushed forward.
"Magical resistance," he grunted, forcing himself deeper. "Because regular Inferi weren't challenge enough."
By the time he reached Regulus, the young man was barely conscious, his face ghostly pale beneath a mask of blood from a nasty gash across his forehead. Multiple wounds on his arms and torso suggested he'd been fighting the Inferi for some time before Marquas's arrival.
"I've got you," Marquas said, hooking an arm around Regulus's chest. "Try not to die dramatically on me now. I've filled my heroic rescue quota for the month. The paperwork is atrocious."
With one arm supporting Regulus and the other maintaining a continuous stream of flame spells to keep the increasingly bold Inferi at bay, Marquas began the arduous journey back to shore. The magical resistance of the water made every step feel like wading through cement, and the rope around his waist, their lifeline to the shore, seemed to grow heavier with each yard.
They were perhaps halfway to safety when Marquas's foot slipped on the underwater terrain, momentarily plunging them both beneath the surface. In that brief second of submersion, an Inferius lunged from the depths, its dead fingers closing around Regulus's ankle with unnatural strength.
Marquas barely managed to cast a severing charm, separating the creature's hand from its wrist, before hauling them both back above the waterline. "Sorry about the manicure, but your nail care routine was clearly lacking anyway," he spat at the retreating Inferius, water streaming from his face.
But the damage was done, the momentary lapse in his continuous fire barrier had given the Inferi an opening, and now they were closing in from all sides, pale shapes moving through the black water with terrible purpose.
"Change of plans," Marquas gasped, tightening his grip on the now unconscious Regulus. With his free hand, he pointed his wand at the shore and shouted, "Funiculus Retracto!"
The rope around his waist suddenly went taut, and they were yanked forward through the water with bruising force as the magically activated rope began retracting itself toward the anchor point on shore. The acceleration caught the Inferi by surprise, allowing Marquas and Regulus to slip through the closing circle of grasping hands.
They hit the rocky shore hard, Marquas twisting to take the brunt of the impact and protect his unconscious charge. Pain lanced through his shoulder as it connected with stone, but he had no time to assess the damage. The Inferi were already emerging from the water, dozens of them advancing with relentless, shambling steps.
"Incendio Totalum!" Marquas cast, creating a wall of flame between them and the advancing dead. It wouldn't hold forever, but it would buy them the time they needed to escape.
Quickly checking Regulus's condition, Marquas found a weak but steady pulse. The young man was alive but badly injured, with multiple lacerations, possible hypothermia, and who knew what magical contamination from prolonged exposure to the lake and its inhabitants.
"Regulus," he said sharply, lightly slapping the young man's face. "Wake up. We need to move."
Regulus's eyes fluttered open, unfocused and dilated. "The... locket," he mumbled. "Got to destroy... the locket."
"Locket later, escape now," Marquas replied tersely, hauling Regulus to his feet and supporting most of his weight. "Can you walk at all? Or shall I conjure a wheelchair with flame-thrower attachments?"
"Try," Regulus managed, his legs buckling immediately. "Sorry... they were everywhere... couldn't swim fast enough..."
"Save your strength," Marquas instructed, noticing with alarm that the fire barrier was already weakening, the Inferi pressing against it with inhuman determination. "We're leaving. Now."
Half-carrying, half-dragging Regulus, Marquas made for the archway that led back to the outer cave. Behind them, the wall of fire sputtered and died in places, pale hands reaching through the gaps. Their escape window was closing fast.
As they reached the archway, Marquas felt Regulus fumbling at something inside his torn robes. "Wait," the young man gasped. "Take this... in case I don't..."
He pressed something cold and metal into Marquas's hand, a heavy gold locket with an ornate "S" inlaid with green stones on its front. Slytherin's locket. The Horcrux.
"You got it," Marquas said, genuine amazement in his voice as he quickly secured the locket in an inner pocket. "How did you—"
"House-elf," Regulus coughed, blood speckling his lips. "Kreacher... knew the protections. Helped me. Told him... to leave me if... something went wrong."
There was no time for further explanations. The Inferi had breached the fire barrier and were advancing rapidly. Marquas helped Regulus through the archway, which sealed itself behind them with a sound like rushing water, temporarily halting their pursuers.
But the outer cave was now nearly submerged in seawater, the tide having risen significantly during their time inside. The narrow exit crevice was completely underwater.
"We'll have to swim out," Marquas said grimly, assessing Regulus's condition with growing concern. The young man was barely conscious again, unlikely to manage an underwater swim in his current state.
Thinking quickly, Marquas retrieved his last prepared potion, a Bubble-Head solution that would allow underwater breathing. He forced half the contents down Regulus's throat, then consumed the remainder himself.
"Hold onto me," he instructed, creating a magical tether between them for good measure. "And try not to drown. It would really undermine my heroic rescue narrative."
With that, they plunged into the churning seawater, Marquas guiding them through the submerged exit and out into the open ocean beyond. The storm had arrived in full force, massive waves threatening to dash them against the rocky cliff face.
It took every ounce of Marquas's magical skill and physical strength to keep them both alive as he navigated the treacherous waters, eventually finding a small cove where they could safely Apparate without risk of splinching in their weakened condition.
With one last enormous effort, focusing on Hogwarts' gates with all his remaining mental discipline, Marquas turned into the crushing darkness of Apparition, dragging Regulus Black, and Voldemort's Horcrux, with him.