"Unicorn hair generally produces the most consistent magic, and is least subject to fluctuations and blockages..."
--Garrick Ollivander (Pm)
Wands with unicorn hair cores are generally the most difficult to turn to the Dark Arts. A unicorn hair core increases the likelihood that a hazel wand will “wilt” when its owner dies (Pm).
- Harry told Firenze that the first-years had used unicorn tail hair in Potions (PS15).
- Mr. Ollivander specified that Cedric Diggory's wand core came from a male unicorn (GF18).
- Slughorn hoped to sell some unicorn tail hairs Hagrid had given him for 10 Galleons a hair. Hagrid collects such shed hair as a matter of course, using it as a binding on bandages of injured animals due to its strength (HBP22).
Cedric, Neville, Ron, and Draco all have wands with unicorn tail hairs in them. This is a bit disturbing because of the following exchange from PS15:
"Yeah," said Hagrid, glancing up, too. "Listen, I'm glad we've run inter yeh, Ronan, 'cause there's a unicorn bin hurt -- you seen anythin'?"
Ronan didn't answer immediately. He stared unblinkingly upward, then sighed again.
"Always the innocent are the first victims," he said. "So it has been for ages past, so it is now."
Cedric, like the unicorn, died. Fans for years worried that Ron might be destined to die as well.