(A/N) Finally. I've been trying to write this for nearly a month now, and it would not work. Feedback would be heavenly. Feed the author. Please? She's beginning to get rather peckish.
Regulus Black, aged eighteen, stood warily in the doorway of his father's study. Not that Orion Black was there; if he had been, Regulus most certainly would not have. But the study was frightening even without it's occupant. It was on the second floor hallway, so that if the door were open, Mr. Black could watch everyone who came up or went down the stairs. It was the darkest room in a gloomy house, the only window cowed and covered by thick brocade drapes, so the old drippy candles were the only possible light source. The candles in Mr. Black's study always dripped, because Kreacher wouldn't crap them like he did all the others in the household. Mrs. Black, in the general way, would not tolerate wax dripped on her Persian carpets. But Mrs. Black had no dominion here. This was her husband's domain, which he ruled as surely as he ruled the account books.
But Orion Black was injured, now, and for the first time in his life, Regulus actually entered his father's study without a direct order to do so. He wasn't sure why he wanted to do so, except that there was so much information to be found here that he might never see otherwise. The walls were covered with dark, heavy bookcases, full of crumbling leather volumes bound up in gold and jewels and curses. This was, as far as Regulus knew, the largest and most complete collection of books of Dark Magic in England, maybe in the world.
So Regulus searched through his father's library, carefully noting where all the books went as he removed them. Then he went to his father's great roll-top desk and sat, even more carefully on the edge of the chair. He hated to read here; it was even more frightening than creeping to the Restricted Section of the library, because Hogwarts was a big place and Grimmauld Place was not and Mr. Black, injured or not, would be on top of Regulus before you could say "Toujours Pur" if he knew that his son was in his study.
He stayed the entire afternoon, reading books and treatises and grimmeries and stories, learning more than he ever had before of the origins of the Old Magic. How Severus Snape would love this library. Regulus thought it amazing enough, because he learned that afternoon, among the blood and vengeance and rights of the Old Magic, where the Crucius curse came from, and how it was related to Imperius and he thought that, if he had several months and could keep this book to study from, he might be able to create a perfect command spell, one that could be used to make anything do anything, perhaps even an algorithm for magic in general. It was a fascinating concept.
The last book Regulus read was called, simply, Immortality. The Dark Lord would love to have this book, and Regulus tried not to notice anything particular about it. The last chapter was on Horcruxes. Regulus read it with the same detached interest that he had read the rest of the chapters, as a dissertation on magic best left forgotten in the practical world. Then slowly, it dawned. Regulus reread the chapter on Horcruxes, imbedding each word in his mind. Memory was not a Black trait, but Regulus possessed it anyway. He thought that perhaps it was because he had no particular driving force, so his mind was empty enough to collect all those extraneous details his cousins didn't care about.
Then he closed the book and began putting all of them away, exactly as he'd found them, his mind busy else ware, in a strange and frightening cave, charming Incubi and watching Snape brew a particular poison from the oldest spellbook the Lord possessed. The book had been burned after, and Regulus had regretted the fact at the time.
So the old locket is a sliver of His soul, Regulus thought as he closed the door of his father's study and went downstairs for dinner. Interesting.