The runes on the stone door began to move.
They slithered across the surface like living things, peeling free from their original positions and rising into the air. Lines of light twisted and recombined, forming an entirely new pattern.
The next second, the stone door slid open to either side without a sound.
Beyond it lay a space choked with gray mist.
The fog was so dense it seemed almost solid, rolling slowly in heavy waves. Through it, faint silhouettes could be seen. Broken pillars. Collapsed arches. A floor shattered into uneven slabs.
Everything was submerged beneath that gray veil, outlines blurred, edges melting into nothing.
But though the door had opened, a glowing magical barrier still sealed the entrance.
It was semi-transparent, like light frozen into a sheet. Silver-white runes flowed across its surface, pulsing at a steady rhythm.
The barrier locked the gray mist firmly inside. The fog slammed against it, ripples spreading across the membrane, but nothing passed through.
Darren stared at the barrier, eyes fever-bright and terrified all at once.
He placed the crystal back into the box, drew his wand, and aimed at the center of the barrier.
Then he began another incantation.
This one was longer. More complex.
Each syllable sounded like it was forced out of his lungs by sheer will. His face drained of color, from pale to chalk white, then to the ashen hue of cold stone.
The hand holding the wand shook violently. The arc traced by the tip in the air wavered and broke, but the chant did not stop.
The runes on the barrier began to flicker.
Erratic and uneven, their silver-white glow dimmed to gray, then darker still.
Regulus narrowed his eyes, focusing his magical senses on the boundary between the barrier and the mist.
The barrier was weakening.
It felt as though Darren was persuading it, forcing its logic to accept that opening at this moment was permissible.
The process was agonizingly slow.
The air in the tunnel grew colder by the second. Regulus recognized the shift instantly. It was not temperature in the ordinary sense, but a change in magical nature.
Through the thinning barrier, the curse within the mist began to seep outward.
It was faint, but unmistakable.
Exactly the same as the curse inside Hermes.
Only this was not a drop.
It was an ocean.
Darren reached the end of his incantation.
With the final syllable, his body swayed. His knees buckled, nearly giving out.
He forced himself upright and pressed the tip of his wand against the barrier.
The barrier turned fully transparent.
Now the gray mist behind it could be seen clearly.
It was not mist at all.
It was faces.
Distorted, twisted beyond human proportion. Mouths split wide in silent screams. Where eyes should have been, there were only hollow pits of black.
And there were not one or two.
There were tens of thousands.
Layer upon layer, packed tight behind the barrier, each one writhing, each one howling soundlessly.
Regulus's breath stalled for half a heartbeat.
Inside Hogwarts, how could something like this exist?
Nothing about it resembled the work of a benign hand.
If one face meant one dead life, then how many had perished here?
The barrier still stood, but its defensive nature was gone.
Regulus forced the question aside. His body shifted subtly into a retreat stance.
Darren stepped forward.
His wand flared with dark red light as he aimed at the center of the barrier, preparing to cast something further.
Then everything changed.
The barrier did not break.
Instead, the gray mass behind it suddenly contracted toward the center, compressing into a knot of darkness so dense it seemed to swallow light.
It froze for a single instant.
Then it exploded.
A visible gray-black shockwave slammed into the barrier. The barrier convulsed violently, fractures bursting across its surface. The cracks spread at terrifying speed, racing outward until the entire barrier was webbed with fissures.
Darren staggered back. His wand flew from his hand, struck the stone wall, and snapped cleanly in two.
His eyes bulged, pupils shrinking to pinpoints. His mouth opened, but no sound came out at first. Fear clamped around his throat.
The cracks deepened.
Gray mist began to pour through.
The first tendril brushed the hem of Darren's robe. The black fabric turned gray in an instant, then crumbled into powder. The dust drifted upward and vanished.
"Ahhh!"
The scream finally tore free, raw and primal.
He scrambled backward, tripping over the stone threshold and crashing to the ground. His palms scraped against the floor, skin tearing. Blood seeped into the dust, leaving dark red prints.
He clawed toward the broken halves of his wand, but his fingers trembled too violently to grasp them.
More mist surged forward. Wherever it touched, the stone floor blackened and decayed, corruption spreading in scorched veins.
The barrier shattered completely.
Regulus's intent to continue observing died instantly.
The stone doorway now vomited gray faces into the tunnel, their twisted expressions radiating a suffocating weight of despair and agony. The emotion pressed into his lungs without effort, thick and crushing.
He slashed his wand through the air. The Disillusionment Charm dissolved at once. He cast the counter-charm on Cuthbert and Alex as well.
Their concealed forms reappeared in the dim light, stiff and exposed.
There was no point in hiding now. They needed to see each other clearly.
Retreat was no longer a precaution. It was survival.
Regulus's gaze flicked to Darren Macnair.
The boy sat sprawled on the ground, clutching the broken wand, flailing blindly. His face was drenched in terror.
Utter fool.
He had prepared only to dismantle the ward. He had no method to contain or retrieve what lay inside.
A thought flashed through Regulus's mind.
Had this been ordered from above? A curse bomb detonated inside Hogwarts?
Voldemort?
No.
Too crude.
And this was Hogwarts.
If Voldemort dared something so blatant, he would be inviting Dumbledore's full wrath.
The simplest answer was the most likely.
Darren Macnair was simply an idiot.
The thought lasted less than a breath.
Regulus pivoted and ran.
"Run."
The word came out low and sharp.
Cuthbert and Alex stood frozen, faces drained of color, eyes locked on the churning gray mass.
Cuthbert recovered first. His fingers tightened around his wand. At Regulus's command, he moved without hesitation and bolted forward.
Alex did not.
His legs refused to obey. He stood rooted in place, eyes wide with horror, breathing shattered and shallow.
Regulus and Cuthbert had already gained several strides when Regulus caught the edge of Alex's unmoving form in his peripheral vision.
He did not turn back.
His left hand snapped up.
"Gripping Charm."
The spell was meant for Gnomes, to seize and fling them from gardens. Against an unresisting student, the force was perfectly measured.
Magic latched onto Alex's waist. Regulus yanked hard, dragging him bodily to his side. His right hand caught Alex's arm in one smooth motion.
Regulus's physical strength far exceeded that of any ordinary student. Even with Cuthbert sprinting at full effort, he struggled to keep pace.
Regulus adjusted.
Another Gripping Charm shot toward Cuthbert, pulling him close as well.
At the same time, Regulus whipped his wand backward and cast Protego.
A thick, solid barrier slammed into place across the tunnel, intercepting the first surge of gray mist.
He followed with two blasting curses at the side walls. Stone shattered and tumbled down, forming a crude barricade.
The mist moved faster than reason allowed.
Within seconds, Darren Macnair's screams were swallowed by the tunnel. High, jagged, filled with terror.
Regulus glanced back once.
Darren's position was already consumed by gray, but within it, a single point of white light flickered stubbornly.
The crystal.
It shared a source with the ward on the stone door. It was resisting, barely holding the mist at bay.
But Regulus had seen the cracks across its surface. It would not last long.
That no longer concerned him.
His only objective was to get Cuthbert and Alex out alive.
He cast Wingardium Leviosa on all three of them, not lifting them fully into the air, but lightening their weight to reduce strain and increase speed.
They raced through the tunnel.
The gray mist pursued like a curse with teeth sunk into bone, relentless.
The stone barricade meant nothing. The fog swallowed it in a blink, leaving no trace.
Regulus's mind raced even as his feet pounded the ground.
The main tunnel here was wide enough. Even hauling two people, he could maintain speed.
But up ahead lay the narrow passage.
The bottleneck.
Only one person could pass at a time.
There was no alternate route.
They would have to slow, pass through in sequence.
And the gray mist would not grant them that mercy.