*Drumrolls* Another Riddler

The answer you’ll be getting is an anagram. The first set of numbers [in square brackets] denotes the length of the answer. The second set – after a hyphen – denotes a letter of particular importance.
It's relatively easier than the previous riddle. But even then, some of it's answers are drawn from deep expeditions into the world of Harry Potter.

1. Result of cross-breeding? Or faulty genetic engineering?
P.S. He’s not a nightingale. [7] – 3

2. No gazing into its deep, deep eyes for sure. [8] - 2

3. We’re sure this spell’d be verrry useful when you have a bunch of Cornish Pixies loose. [10, 10] - 10

4. If she’s as vain as that Greek guy, she’d better learn swimming [8] – 6

5. The toilets are not THAT private a place with her around [7,6] – 13

6. T’is easy. A Prankster, a Poltergeist … [6] – 6

7. Opiumated and nursey [5,7] – 6

8. She can chase well. Better than an angry bull when it comes to large, red balls [5,4] – 7

9. Not as sinister as her name, surely [8] – 3

10. Ve(e)la girl [5] – 5

11. I swings more than mood swings [5] – 3

12. Acrophobia and motion sickness has no place here [9] – 7