OD: Secrets of the Darkest Arts
Gideon took the book when Minerva offers it to him. He examined it, visually and magically, to make sure it was safe before he laid it flat on the table where anyone who wanted to join him could also look.
The book was large, hand-written, and bound in faded leather. The anonymous medieval writer's hand was shaky and the letters resembled distressed spiders, but it was readable. Dumbledore's notes helped.
"This is abominable," Gideon said, "Yes, after the murder and the spell, the caster places the soul in a relic of some sort. The object becomes extremely durable. One way to tell if you've found one is that you can't destroy it by normal means. The author found that utterly hilarious, apparently."
Gideon turned a few pages. "OK, so the horcrux -- horcruces, I suppose. Anyroad, they can affect your mind and bend you to the will of their master, and eventually allow them to possess the owner. It withers the body. Anyone here read Professor Tolkien? This sounds really familiar.
"Oh, and to make matters especially lovely, it's possible to regenerate the body of the deceased Dark Lord, although the potion is far beyond what I could or would do."
Gideon swept his hands through his hair, looking back at the Chief Mugwump's notes. There wasn't much to go on.