I don’t see why bone would be difficult, given that it doesn’t have to be taken from a living ancestor. Not unless Dumbledore prepared for this and warded their graves.
Harry’s unable to leave Hogwarts. There could be ways around the restriction, but they add complexity to the solution.
ETA: Which, to be clear, looks completely unworkable on its in-universe merits. The real problem is that Harry’s never heard a full description of the ritual, neither Dumbledore nor Voldemort would give him one, and Voldemort would have stolen the book that contains it.
I don’t see why bone would be difficult, given that it doesn’t have to be taken from a living ancestor. Not unless Dumbledore prepared for this and warded their graves.
Harry’s unable to leave Hogwarts. There could be ways around the restriction, but they add complexity to the solution.
ETA: Which, to be clear, looks completely unworkable on its in-universe merits. The real problem is that Harry’s never heard a full description of the ritual, neither Dumbledore nor Voldemort would give him one, and Voldemort would have stolen the book that contains it.
Then again, it could be “bone of a living ancestor, unknowingly bequeathed”. Now we know why Madam Pomfrey’s the one in charge of the Grangers...
Voldemort’s father’s bone is sufficient in canon. Tom Riddle Sr. is long dead.
Then why would they have been poisoning the bones of Voldemort’s dead ancestors?