As ever, standard disclaimers apply.
Dumbledore had originally thought to send only Kingsley Shacklebolt inside Malfoy Manor with Severus, but Bill Weasley had quietly reminded him later than his own expertise at curse-breaking might be a useful adjunct. Molly wasn't very happy, but as Bill was (and had been for a number of years now) an adult well able to make his own decisions she'd said nothing in disagreement. This did not mean she kept her worried opinion to herself. Not with that pinched expression she wore! The Headmaster could only sigh in remorse that so many good people had to put themselves in jeopardy for a world which seemed not to care. As for himself, he could only wait for some word...
--
He strode ahead as if familiar with the passage. In fact he wasn't as he'd only made the one visit during a childhood now only recalled with the same unexpected gaps as the rest of his memories. But strangely, he felt no sense of hesitation, nor any fear of becoming lost. As well, he had companions, (an Auror slightly older than himself and a curse-breaker slightly younger), before whom he would never deign to show any reticence. He might have wondered at any meanings of this juxtaposition of their ages but he'd not the inclination and likely would have rejected such assertions as quite preposterous. Severus Snape was not a man who concerned himself with the useless ponderings of meaningless symbolism where, in fact, none existed. Just as, in his mind, with divination which, if it was effective at all, merely served as warnings of possibilities. And those were, often as not, mere distractions.
He could not afford to be distracted.
Instead, he lead his two companions with single minded resolution onwards, deeper into the bowels of the earth, closer to a mystery unsolved. The musty stone walls had quickly deteriorated into hard packed dirt, held from falling by some ancient magic no longer well known, and then, as they descended deeper, became chiseled bedrock. The internal temperature had leveled off to something quite cool and made to seem even cooler by the ambient humidity and it had remained unchanged for the last half hour of their downward hike. Indeed, they were still moving steadily downward through the passages, his companions not in the slightest reassured by Snape's apparent disinterested disregard to the occasional side passages and turnoffs that he didn't take. Both of the other wizards silently accepted his terse explanation that these were mostly tombs and vaults but also tunnels that turned on themselves, misleading the mind's sense of direction.
"However, did you find your way?" Weasley, who occasionally paused now and again to lay down invisible magical markers, asked at one point.
The Potions Master halted abruptly and turned back to face the two other wizards. "Do you not feel it?" He asked incredulously, dark eyes glittering despite the shadows cast by their faintly glimmering wandlights. "Do you not feel the magic pulling at you?"
The Auror and the curse-breaker shared a dubious glance with one another. "Whatever you sense, Snape, I do not." Shacklebolt admitted. "Describe it."
"I cannot. It simply is."
"Is what?!" Bill insisted with great consternation.
Snape grimaced and leaned wearily against the bedrock wall. "Magic, you dolt. How can I explain it if you cannot feel it?" Truly he was not fully recovered and it could not have been more obvious. Yet he had not the energy to pretend.
Bill quite obviously strained to hold back his own sharp retort.
Shacklebolt was less moved to react. He simply asked, "Dark?"
"Neither dark nor light." Snape frowned as something occurred to him and he added in a low, respectful whisper, "Old." Then he pushed off the wall and resumed gliding down the passageway, oblivious to whether or not Weasley and Shacklebolt followed. His breathing became labored and the sound echoed back to his companions who hurried to draw alongside him. The large Auror grabbed his arm, forcing him to a halt. "Severus, sit down for a bit, before you fall down."
"You can't go on ahead. You will most likely run into Death Eaters. Or worse."
"We know that, Snape." Shacklebolt tugged again on the Potions Master's arm. "We aren't going on ahead."
Snape meant to snarl. Instead he sighed and accepting the Auror's assistance, lowered himself to the ground and leaned back against the rough wall, closing his eyes to rest. Knowing that the Dark Lord was not going to greet him with any great cheer he realized that having some reserves of endurance to call upon would be a wise forethought. In a moment he'd rifle his pockets for the energizing potions Poppy had left for him.
Rough scraping whispered about his head as the other two settled down beside him but he didn't bother to open his eyes. Nor did he open his ears but rather did his best to ignore the snippets of sound that comprised their quiet, furtive, and very sparse conversation. "I do not remember you," he murmured at last, without bothering to look and see if either heard.
"What?" Bill's voice responded from the slight distance across from him.
"Hm," Shacklebolt's response gave no indication to his thoughts though it did reveal that he had seated himself close beside the Potions Master.
"I remember Remus. Lupin" He grimaced at conflicting emotions the man's two names brought forth.
"And my mum, I hope."
"Yes. Though not much from before..." His whisper trailed off.
"Dumbledore?" Shacklebolt asked with mild curiosity.
"Oh yes. Quite. Vividly in fact." He shifted on the ground as if such would alleviate his discomfort. But a stony ground was not meant to be any sort of comfortable resting place and neither would he allow the Headmaster any role of comforter.
"Who else?" the younger curse-breaker asked.
"Potter." Came a hard growl
"Which one?"
"James, of cour--. Oh. Harry." There was definite confusion and no hint of spite all of a sudden. "James is dead."
"Hm," Shacklebolt mused softly again. And he changed the subject. "You still sense this old magic?"
"Yes."
"Do you suppose this old magic is what You-Know-Who is after?" Bill asked still trying to see past the opening.
"I don't know, Weasley. Why don't you go on ahead and ask him?"
"Tempers, gentlemen." Shacklebolt warned before Bill could come back with a retort.
Snape let himself breath a deep sigh before opening his eyes. Then he brought out one of the vials of potion and studied its contents in the faint wandlight. It seemed satisfactory, assuming he could trust his recall of his field of study. And he thought he could. He set his still illuminating wand down beside him, needing both unsteady hands to uncork the crystal container.
"What is that?" Shacklebolt demanded curtly.
"A potion for enhancing the drinkers energy." Snape explained without his usual rancor just before swigging down the dark colored concoction. He coughed and wincing, shook his head. "Too sweet," he muttered, his face still screwed up in distaste.
He shoved the vial back into a pocket only a moment later and sat up straighter. "But not completely without efficacy." A moment later he'd pressed his fingers against the rock and used the pressure to help him regain his feet. "Are you coming?" He pushed away from the wall and resumed the trek confident the other two would catch him up quite quickly.
He led them through twists and turns that Bill Weasley thoughtfully marked for future reference and finally turned off into a very narrow tunnel that forced all three to hobble bent over into uncomfortable contortions. Bill was the shortest but by no means the most slender so it was no easier for him than for Snape who was tall but quite thin. Shacklebolt was the worst off as he was both broad and tall. But none of them voiced any complaint. There wasn't time. This narrow tunnel snaked straight ahead for several yards then abruptly ended. Snape turned to his right, at last coming to a halt.
"Is this where it's blocked?" Weasley's voice broke the silence.
"It was," Snape replied. "But no longer." He stepped forward without any warning and as he squeezed through the narrow opening heard the others gasp as the light from his wand disappeared from their view.
"Snape!"
"Quiet," he hissed back. "Do you-- "
Bill Weasley was just working himself through the opening when the universe exploded in a cacophony of brilliance and ear-shattering shrieks. He gasped and felt something pull him backwards. The rock scraped and scratched his clothing and arms as he fell backwards against the massive chest of his would-be rescuer.
"Sh!" Shacklebolt hissed softly while shoving the younger man sideways against the wall.
As ordered, Bill was silent. Except for the pounding of his heart and the ragged breaths of diminishing panic.
"What happened?" The Auror whispered after several thankfully uneventful minutes of silence passed.
"I don't know. I didn't see anything!" He leaned around the larger man but to no avail. All was dark and his eyes were still far from dark adapted. "What about Snape? Aren't we going in after him?"
"Yeah. I am. You wait here. Be ready to apparate on my orders."
Kingsley Shacklebolt worked himself through the opening cursing the tight fit only in his head. When he finally popped through he barely managed to keep from stumbling. But despite his bulk and size, the Auror was not an ungraceful man. He had an excellent sense of balance that he expected would serve him well in this thick darkness. He turned about in place and learned nothing. Except that Severus Snape was not unconscious at his feet. And there was no sign of Voldemort nor his Death Eaters (Thank Merlin for large favors.) He placed his free hand against the wall and was surprised to find it smooth as glass. He brought his wandlight closer and peered at the surface. It was not stone. Nor wood. He frowned. Metal? But it was not cold as metal would be. It did not leech the warmth from his palm he laid across it. Never mind. First things' first. Snape.
"Lumos!" Shacklebolt demanded a stronger incandescence from his wand. Still it was not enough to illuminate the chamber in its entirety. It was enough, however, to tell him two things. The first was that the chamber that had found was definitely not a natural formation. The second was that Snape was no longer with them.