Is she dead?

Well, regardless, I will attempt to give you constructive criticism, but because it is 'that kind' of story, I am going to be particularly brutal.

Let us begin.

First: Where did you pull this Luna from? If you truly wrote this in December of 2011, "Luna Eclipsed" had already aired, so Luna and Twilight would have already been somewhat friendly. Second, in "Luna Eclipsed", Luna exhibits no malice towards the populace even when she is shunned. Sure, she's extremely disappointed and flummoxed, but she doesn't ever do anything even approaching this.

Next up, Twilight. First: she has a multitude of friends who would have noticed her missing. Even skimming the other chapters, some of which appear to occur a day later, there is minimal mention of Twilight missing. Next up, Spike would have noticed her missing immediatally.

Why exactly was it necessary to kill her? I mean, you literally give no explanation as to the purpose that served. She was also being guarded by the guards, AND Luna appears to have wanted her alive (or she would have killed her already). So basically, killing her was terrible for the viewer, stupid and unhelpful to Luna, and traumatizing for those who love her. As such, I must assume that Twilight would have rendered some of the plot null: either through her knowledge, her friends, or her element. However, this is, quite frankly, a very cheap trick: You don't actually explain how she was captured in the first place, and you render her completely incapacitated through means of an off screen character. Killing a character in the manner you did earns you some visceral emotion from the reader, not unlike the 'jump scare' tactics employed in many horror films. While it 'achieves' an emotion response, it does so by appealing to baser instincts.

An addition to the above: How does Twilight move so far, so fast, with such grievous wounds? That part was, in my opinion, completely out of place. Sure, you may have added suspense - as the reader thinks that maybe Twilight has a chance... but it makes no sense in the context of the story. Furthermore, the whole 'escape and recapture' shtick has been played to death in recent years, so the absurdity of having a heavily-bled Twilight able to perform such amazing feats to even allow this to happen is even more grating.

Then you have the fact that Luna *apparently* took Twilight to a torture chamber that Canterlot has for some unexplained reason. Oh, and Celestia is no where to be found during this whole event. You could have added some sort of line explaining why Celestia doesn't appear to be present. Further, I think KILLING the bearer of the Element of Magic would register on someone as powerful as Celestia, and she would use her long range teleportation to end Luna.

Speaking of the Elements, here is another problem: The Elements do not bind based on whether their 'owner' is alive, they bind based on another (unexplained) reason. By committing these crimes, Luna has sealed off the Elements from ever binding to her again. After all, it is only because of her relationship with her sister that that the Elements bonded to the pair during Discord's rule. Without it, the Elements would probably bind solely to Celestia... which is the opposite of what Luna wants.

And another problem: If Celestia is weaker than Luna, then the plot could not happen as it has. After all, if Luna actually IS stronger, she could just usurp the throne without aid. If Celestia is stronger than Luna, then she probably would have stopped this atrocity from happening.

I decline to rate this piece. Frankly, it reads more like a torture scene that was hastily given context rather than a story that happened to have a torture scene. The only way to curb that would be to provide an adequate lead in to the story. As it stands though... it's just so pointlessly brutal.

Even IF i granted you a Luna with a personality that saw her sister as weak, she still wouldn't act like this. She wants to be ruler, and (presumably) loved, so this wouldn't fly. She wants to protect her kingdom, yet nearly kills the bearer of the Element of Magic through torture, which she wouldn't be stupid enough to do. She wouldn't be foolish enough to think she could break Twilight either: she'd either kill her and be done with it or not waste her time trying. I mean think about it: by torturing Twilight she runs the risk of alerting Celestia to her coup, OR (more reasonably) pissing Celestia off to the point she kills Luna in unbridled fury. Neither of which fit with a cold, calculating Luna.

The whole thing is just so over-the-top that it completely detached me as a reader from really granting it emotional investment. It's like my brain just went "You know, this can't really be happening, because none of the characters are making any sense." And this is before I even officially read the part with Applejack!

Apologies for the harshness, but these sorts of tales have to be written almost flawlessly to really get the reader to feel for the characters.