(A/N: Bellatrix only showed up at the very beginning of HBP. My take on why, uh, because. And I hate that ending, but couldn't come up with better. Review! Even if all you write is, 'DAMN, that sucked.' I don't care. Just say something.)
Once-upon-a-time, she loved this. A regular Marquis de Sade, high-ranking among the minions, more vicious, more cold than the rest. It wasn't a secret, and she wore her insanity proudly - going to prison for it, killing her cousin for it, tackling any enemy her leader saw fit - all to...
And there's that weak spot, that Colossus-knee, the question she can't seem to forget - but... why? She has the answer she's always had, they've always given her - of course, to purify the Wizarding race.
But... why? Why do they all have to die, and why... Why does the Dark Lord need immortality to do it?
There was a time, a place that she relished this - this was her life and she was happy in it - but the rest seeps in unheeded, unchecked, a shameful memoir of the things she thought she left behind long ago.
Her sisters (plural, yes, plural - she has two, two sisters, more than just Narcissa, but she can't quite bring herself to remember her other sister's name, not now, not after Azkaban, not after everything) used to play with dolls in the drawing room and she used to think they were stupid and why play with dolls when there were so many more interesting, exciting, dangerous things to do with her time? And now, now she thinks she wasted her childhood, wasted the only pantomime of innocence she might have had, wasted it on spells and magic tomes, because, because, because...
There is no because, no answer, no reason.
She did it because she thought it was right, and it was wrong, but she excelled in her classes for it, right? So it couldn't have been so bad, except... Except Cissa excelled in her classes, too, and Cissa played with dolls and dresses in the attic with Andr-
No. No Andy anymore, remember?
Once-upon-a-time, her life was pain, inflicting it, feeling it, loving it, hating it. Her virtue, her vice, her weakest point and highest strength. In exchange for power, she gave up her soul - in exchange for strength, she sacrificed all of her lacking humanity. Regret, yeah, regret. Andy knew regret, Cissa knows regret, Sirius, even Regulus knew regret.
What's wrong with her? Why is she the heartless sadist Death Eater?
Once-upon-a-time, she was a powerful Death Eater, a great murderer, an infamous criminal, on top of every list. Once. Now, though, a has-been who nearly got beaten in a duel by her stupid niece, a pathetic remnant of terrible beauty wishing upon the ghosts of a past long gone, haunted on every step by the questions she never thought of when she could think.
She's cracking, she thinks, the same way they say Sirius cracked - right at the seams, right on the faultline - and it leaves a raw, bitter taste in her mouth. No longer the favorite, now too old, too well-known, too many demons on her back. She's been left alone too long, left out to rot, and she realizes, belatedly, that they all end up like her in the end. Cast aside for newer, better, stronger, faster, more ruthless, more sadistic, more powerful - left to congeal, left to break apart at the cracks that have always been there.
Once-upon-a-time, this was her life. Now rubble, now ruin, now remnant, and even Andy-with-the-brown-hair and Cissa-with-the-blonde won't play with her now.