Disclaimer: Harry Potter belongs to J.K. Rowling. I make no claims to ownership.
No one knew the location of the manor. The Death Eaters simply followed the call of the Dark Marks and showed up there every time they were summoned. Snape had been in the middle of an experiment when he felt his Mark burning. As a result, he was rather irritable with the summoning, but thankfully his mask covered his expression as he entered the throne room.
His eyes swept the room and noted that it was absent of anyone but him and one other person. At the front, languishing on the throne, was a tall, pale man with thinning dark hair. Snape had always wondered just how old the Dark Lord was. His closest advisors, those who belonged to the Knights of Walpurgis, were tight-lipped about his origins; Snape suspected they were under an Unbreakable Vow.
He wished he could use the vow on his fellow Death Eaters. That or use Sectumsempra so he could watch theme bleed out at his feet. Then they would stop mocking him for his love of a Mudblood.
"Ah, Severus," a soft, cold voice said from the throne; the Dark Lord's red eyes were glittering with amusement as Snape knelt before him. "So violent, aren't you?"
He ducked his head, fighting the urge to clench his jaw. Even the best Occlumens would have trouble keeping the Dark Lord out of their mind. Snape, who had no training at all, knew he was defenseless.
From the throne he heard a rustle of cloth and then the Dark Lord's boots appeared in front of him. The mask was torn from his face and long, thin fingers wrapped into his hair. Helpless, Snape was forced to meet the Dark Lord's gaze.
"Yes," he whispered. "It is as I thought. You still desire her, so much you would kill her husband and child and take her for yourself. A rather strange mind you have, dear Severus."
The name sounded mocking coming from his mouth. Spots of color entered Snape's cheeks. Names had power in the Wizarding World and he was trying the best to live up to his own. The emperor for whom he was named had claimed power after deposing of all of his rivals.
"I have a way for you to do that," the Dark Lord said, reading his thoughts again. "But first you will make a vow, Severus, to always serve me. Any information you hear from Dumbledore will be given to me, and in exchange, I will spare your little Mudblood."
As the fingers tugged roughly on his hair, images of his meeting with Dumbledore flashed through Snape's mind. He should have known the Dark Lord would find out about his duplicity. Potential traitors were always dealt with before any real damage could be done. This was the first time he'd heard of a traitor being spared, though.
"Yes, my Lord," he said, lowering his gaze in supplication and swallowing hard. "I'll do anything. Just – please. Let her live."
The Dark Lord's lips twisted into a mockery of a smile. Sudden pain ripped through Snape's left forearm, but he didn't cry out. All manners of spells could be done through the Dark Mark. He knew he would die instantaneously if he tried to betray the Dark Lord again.
When the spell was complete, the Dark Lord released him and went back to his throne. From there he observed Snape, his red eyes glittering again.
"Because you gave me the prophecy and because of the spells you have given us –" He flicked his wand and Snape was jerked up into the air, dangling above him. "– I have decided to spare you. Do not waste this opportunity, Severus."
"Yes, my Lord," he gasped out as the blood rushed to his head.
He would do anything so he could have Lily, even if it meant suffering this humiliation again.
Almost fifteen years had passed since that meeting. Now Snape sat before Dumbledore's desk instead of facing the Dark Lord. They were alone in the office except for the phoenix, Fawkes. The creature was molting and looked like it would burst into flames at any moment. Dumbledore was twirling one of the feathers in his hand, his expression inscrutable even to Snape.
"Tell me, Severus," he said softly. "What do you know of the Black family?"
"They're arrogant, conceited morons," Snape replied immediately with a sneer.
From one portrait came, "Using creative words doesn't make you any wittier," which he studiously ignored. Ever since the death of his great-great-grandson, Phineas Nigellus had been producing a constant stream of testy comments. Most of them were directed at Dumbledore but he also blamed Snape, who had purposefully delayed reporting Potter's escape to the Ministry instead of trying to help him.
The portrait had tried to convince Dumbledore to release Snape, but the fool still insisted he was trustworthy. Even Snape couldn't fathom why. He'd done the bare minimum to be helpful since he'd agreed to become Dumbledore's spy. In fact, he'd done more damage than aid: several important allies had died because of him, like Black, Vance, and Bones; he'd driven all of Slytherin to the Dark Lord; and because he'd flunked most of the students, the Auror force was smaller than ever.
Yet Dumbledore never questioned him. Snape suspected the old man had become senile after the last war.
"That's enough, Phineas," Dumbledore said, throwing the portrait a severe look of reproval. "What I meant, Severus, is what do you know of their history?"
"Black was the last of his line," he said. "What does it matter?"
Instead of answering, Dumbledore released the feather; it crumbled to ashes as it left his hand. With a flick of his wand, he summoned two files from a cabinet. Opening them, he then lay them out in front of Snape, who dutifully bent to inspect them.
Snape paled. "That's impossible!"
"It is not," said Dumbledore. "The Black family disowned their disgraces instead of killing them. It ensured the family continued, even if it was tainted."
"What are you saying?" demanded Phineas Nigellus loudly.
The other portraits were no longer pretending to be asleep. They gripped their frames and craned their necks, trying to view the files.
Snape's hands clenched into fists.
"There can't be any more Blacks," he snarled. "The dog said so himself!"
"Sirius wouldn't have been aware of it," Dumbledore explained. "Phineas the Second was disowned for marrying a Muggleborn witch. They then left Britain and were never heard from again."
His expression was heavy, but Snape didn't care to analyze it. He was still trying to process the information. Only a day ago, he'd felt vindicated for all of Black's misdeeds against him. The line had been obliterated from the Earth because of him. Now he found out all of his effort was for nothing.
In a surge of anger, he stood from his seat and began pacing. He knew his emotions were written on his face. Fortunately the Dark Mark prevented Dumbledore from reading his mind; he'd been glad when the Dark Lord returned and renewed the spell, as it meant he no longer had to be on guard around the Headmaster.
"They must have fled to Denmark," Dumbledore continued. "The line then combined with the Astorsens, who are also related to the Greengrass family. It was Mrs. Greengrass who requested the student transfer."
Snape swung around. "Why are they transferring now, in the middle of a war?"
Dumbledore sighed and looked away from him, out the window overlooking the sprawling grounds of the school. He remained quiet for so long that Snape's temper almost snapped.
"Unfortunately, I can think of only one reason," he said at last. "The Greengrasses didn't take part in the last war but it's possible they've now sided with Voldemort."
He paused as Snape flinched. After a disapproving frown, he continued.
"There's also the matter of the Black inheritance. With a living Black within Britain, Harry can't inherit the house nor any other property from Sirius. That means we can no longer access Grimmauld Place."
Snape crossed his arms. "And they have control of the house-elf," he noted.
"Indeed," Dumbledore said softly. "They must be monitored, Severus. I'm relying on you to do so."
After a moment, Snape nodded. He wouldn't be doing this for the Headmaster, though. The Dark Lord had promised him retribution, and Snape would achieve it no matter the cost. He couldn't wait to see every Black and Potter dead.