Spike had spent the last few weeks poring over every History of Magic text she could lay hands on, chasing the wild footnotes, seeking in ever more obscure corners of the library. Some of the references she really needed had been destroyed or permanently mislaid, and she had become very good at explaining to the Room of Requirement what she needed in order to continue her research. "Could I possibly have the 1843 edition, please, the one that wasn't bowdlerized in the Subsequent Unpleasantness?" and the text would swim and flow before her eyes. So long as she left the books in place, the Room seemed to have no problems providing the required texts.
The one time she had tried to take a book with her (it was getting late, and she was going to barely make bed check) the Room had sealed the door, simply absorbing it into its walls. No matter what Spike tried, until she set the book down in the middle of the room and walked to where the door should have been did the castle let her go.
She closed the heavy cover of the book, gave it a reluctant pat goodbye. That's it, then. I now know as much about making Horcruxes as any wizard ever has, maybe as much -- maybe more than! -- Riddle himself. Nothing to it but to do it.
Down to the labs in the Snake Pit, where she had carefully laid by ingredients. I'll start with an animate Horcrux, I think. Something upon which I can lean and draw energy from, something I can use as an extra pair of eyes and ears. She was reluctant to use a snake; something from the same phylum just seemed too awfully close to using another sentient being. She could see that chain of reasoning from a snake to a rat to a monkey to a child. Something like what the good Doctor Wolfgang would come up with. Something like the Knights of Walpurgis would decide -- Muggles aren't wizards, animals are not wizards, Muggles are animals and thus it is right and proper to use them as you would . . . an animal.
But an invertebrate should be safe enough. No brain to speak of, just handful of connected ganglia. She had found a Flesh-Eating Slug in the garden, fed it on bits of steak and kidney swiped from dinner's pies to tame it, and had worked on training it to do simple commands. Having something small and squishy that can fit into nearly any space should be a useful being to have as an assistant.
Using the magnetized chalk in its silver holder, she drew the diagram on the floor, laid the pinch of powdered unicorn horn to the north, the manticore venom to the south, the polished moonstone for the east, and the volcanic ash to the west. Earth, air, fire, water. She picked up the cage with the slug, stepped into the center. And spirit. She drew the final symbol to close the diagram and watched as it flared electric blue and faded, leaving only the dazzling purple after-image dancing before her eyes.
She sat carefully so as not to smear her work. At best, she would have to start all over again . . . at worst -- she pushed the thought out of her mind. Intent is everything. Don't bring an intention of failure with you.
She set the cage across from her, pulling a candle out of one pocket, lighting it wordlessly and setting it between them. The slug's eyestalks retracted, and it hissed its displeasure at the bright light. A moment passed, and it extended them once more. At the same time, Spike pricked her finger with a sharp needle, let a drop of blood fall on the slug, then pithed it expertly as she muttered the closing charm.
One heartbeat, two, three, a dozen. Her heart sank. It hadn't worked. All of this for nothing . . . Then the slug's eyes opened again and it blinked up at her. Silver streaks raced down its flanks and its mouth gaped open as it smelled the blood on her finger.
Spike let it lick the pinprick; its saliva numbed the sting. "I did it. I made a . . . well, not a real one, but well, close enough. Close enough to do what I need it to do." In that moment, she understood Dr. Wolfgang, understood him very well indeed.