Artist's description:

So I really like evil and angsty Twilight and hope this art conveys the story good enought.
… “It was all in vain” Twilight thought, as the celestial spear entered her chest, burning with ethereal heat. “Bravo, my teacher. I messed up, and you still managed to find a way to take revenge on me, even in death. You never liked losing and made sure you wouldn’t be the only one who lost. I should have been prepared for that, but what does it matter now?”

She saw Dash’s face, tears in her eyes, yet didn’t hear what she had screamed. “Did I get betrayed by the Element of Loyalty, or was it me who betrayed all that our friendship had been built on? Regardless… now with no other alicorn to rule, Equestria chose to subject to a foreign force, rather than to be ruled by a Dark Princess. Such are ponies, I suppose…”

As the two fell from the sun-lit heights, through clouds and onto the ravaged lands of their country, Twilight’s strength was leaving her.

She whispered to her assassin:

"I’m sorry for all of the suffering I caused. I am a monster, and monsters deserve to die… Thank you."

As the Usurper fell into the magical blue fires burning Canterlot, the mighty griffin army approached from the east, and the few troops still loyal to Twilight Sparkle saw their leader’s demise… The thousand-year rule of alicorns was over…