Description pull:  
“Life’s end. Isn’t it beautiful? Isn’t it tragic? When life ends, it gives off a final lingering aroma. Light is but a farewell gift to those waiting to die.
 
“I’ve been waiting, Twilight. For a long time. Waited for your birth, your growth. And now: for the finality of today.
 
“Why? Because I can no longer bare the elements. They were once a part of me as they are now you and your friends. I am happy. But inside I am saddened for myself. I am not the princess I was, or can be for any longer. But with the end of my sister’s madness, I could feel the elements slipping from me. I had extended their purpose. And in the end I knew they’d need to be a part of somepony else. Who: I would need to wait. But that who would be great.
 
“The foibles of politics can play hard on a Princess, and I have feared that I have not become as pure as I was. I was kind, yes: but only to my subjects. I did tell the truth: but I lied to defend them from the most damaging of truths, or withheld it. I was loyal, but in the end unto myself first, and my ponies lastly. I was generous, but only to reward in bias. My laughter and my smiles felt false, reduced to ceremony and untrue; I wasn’t happy. And in these last days I have learned, that my magic is now only secondary to another.
 
“I felt my friends turn to enemies, and I becoming less of a leader. I was held as a God. But it felt false. Ridiculous, isn’t it? And in my rule, my virtues have been replaced merely with the inevitability of politics without the guidance of a virtue. Yesterday’s enemy becomes today’s friend and I played them as such. To maintain the status quo.
 
“Think back, Twilight. With what you know now and with what you felt, could you ever say I was true? Was I really the hero? Or was I lie to myself, you, your friends. I and my sister are as little it feels. Can I be that again in this coming era? The elements have moved on, and I am as much a token of the past as of Three Kingdoms.
 
“Can the elements be played like politics? Somehow I doubt it. They do not follow the flow of the ages and the march of the times. They have their own mind. And we ponies are forced to play along. Not just for Equestria’s good: for all the good.
 
“I didn’t tutor you and shape you this way just so we could face each other in battle. A Princess’s skills aren’t meant to be used to hurt friends. But, is there such a thing as a timeless and absolute enemy? There has been no such thing, and never has been. But maybe you can prove that wrong, and redeem my spirit.
 
“Do you see the emptiness of my self? No regalia. No crown. No regrets. I have thrown aside the duties on me. But I still feel them churning inside. The same feeling I had when I still wore the regalia. I have lose something different. They were a sign I was something greater. But I sacrificed them all in the name of the Greater Good. My maredom. My princesshood. My divinity. But I still feel the emptiness gnawing at me.
 
“…
 
“I have never talked about myself this much before. Thanks… Thanks for listening. I feel… content… Twilight…
 
“<Commence the operation>
 
“Twilight. I have given you your skills. You friends. Your life. Taught you techniques and helped endow you with more knowledge than any student in my school would ever hope to grasp. I have shown you the path you so dutifully and righteously explored. You have gone above and beyond many ponies your age, or even in your era. You and your friends. Twilight, I have nothing left to give, except my life. By your own hoof, and horn, and magic. One must die. One must live.
 
“You must learn the final lesson: Sacrifice. A reign’s end.
 
“The one who survives must inherit the title of Princess. And the one who inherits the title of Princess must face a life of embattled existence.
 
“I’ll give you ten minutes.”  

 
In part inspired by maddened late-night discussions with my friends about the corruptibility of the characters of MLP. More specifically the deeper troubles that no doubt surround Celestia. Not so much she’s dark. But as far as the show goes: she can no longer use the elements which suggests they have abandoned her in some way. Which might suggest she hasn’t been pure to their cause. In an essence she has become to the virtues as some characters from the Fallout Equestria universe has become to the six virtues.
 
All of which is a crazy fun head-canon my friends and I will occasionally go on about. So enjoy it in Metal Gear form.