The tiara clattered loudly as it landed in Celestia's cell. She almost tried to raise it with her horn, before remembering, and lifted it in trembling hooves instead. 

Dry, red flakes crusted the golden circlet, and the tips of the seven-pointed star. In the violet gemstone's facets, she saw her reflection, and watched tears streak down her pale, emaciated face.

"You wanted proof." Her visitor said the words gruffly. "She didn't suffer, if it helps."

Celestia wrenched her eyes shut. She fought, and failed, to muffle her sobs; they echoed about the cavernous maw of Tartarus.

"Guess this means there's no chance of us catching up over tea?" The usurper snorted; Celestia heard her hooves clop against the rocky terrain as she turned to move away. "I guess that's fair. Stew in your grief and your hate, 'Princess.' I'll be seeing you."

Celestia spoke, without thinking. "I never hated you, Sunset."

The hoofsteps stopped. Celestia opened her eyes, and saw the blood-red alicorn staring quizzically back at her.

The Princess swallowed, and mastered her sobs long enough to gaze placidly at the usurper. "I only ever pitied you."

Sunset Shimmer's cat-slitted gaze hardened. Her mane, a tangle of red and gold flames, blazed brighter, hotter. "You [i]pitied[/i] me?" she said, a razor's edge in her voice.

"I did."

Uncertainty dulled the razor. "Even now?"

"Now, more than ever."

Sunset narrowed her eyes. "Why?"

A hoof, shod in a tarnished, golden boot, stroked the edges of the seven-pointed star. 

"Because you never had what she had."

"You're gonna make me ask, aren't you?" Sunset turned and spat a wad of saliva that crackled and fizzled as it ate through the rocky ground. "Fine. Enlighten me, teacher. What did Princess Twilight have that I, apparently, am so desperately lacking?"

Celestia let a moment pass. "...Friendship."

Sunset Shimmer laughed harshly. "You sad, deluded, toothless old relic. I clap you in chains and throw you in Tartarus, and you think it's, what, a cry for help? That I'm – [i]heh[/i] – that I'm lashing out because I didn't make enough [i]friends[/i] or get invited to enough [i]birthday parties[/i] when I was a filly? That this is some kind of temper tantrum?!"

"That's all it's ever been, Sunset," said Celestia. "Your pursuit of power, your fall from grace – it's all because you were too afraid to reach out for what you truly wanted. What you still want, I think."

"As if what you think matters," Sunset snapped. "Your protege is dead, and your sister's off farming moon rocks. The rest of your family, and those simpering Elements, are crow-food in their gibbets, and Discord's a statue soaking up crow crap beneath 'em. Your kingdom is [i]my[/i] kingdom now, and you?" 

Sunset suddenly unfurled her leathery wings and sped up to the bars of Celestia's cage, slamming herself against them and pressing her face close between them. "I used to hang on your every fucking word. Now, you're nothing more than a trophy. A toy. At best, a pet. Piss me off, and I'll have what's left of your head."

"With my dying breath, I'd still pity you. Do you know why?" Celestia gazed levelly at her fallen student. "Once, you could have had what your heart desired. But that road is closed to you now, I think. Never to reopen."

Sunset grinned a mouth of jagged, pointed fangs. "How tragic."

"More than you know." Celestia bowed her head, baring a broken horn to Sunset. "Because, one day, you're going to come upon someone, or something, that you can't consume or destroy – something that only love can truly drive out. In that moment, you'll despair at what you've given up, and you'll know how hollow your pursuit of power truly was."

Sunset's eyes widened, minutely, for an instant. Then she curled her lips back and sent a wad of burning spittle splattering against Celestia's cheek. The Princess took it, unflinching, even as her skin seared and crackled, her cooked flesh tickling her nostrils.

Then Sunset pulled back, and strode away from Celestia's cell. "Good talk, teach. Let's have another, real soon."

Celestia waited a long, long time, until Sunset, and the fire that trailed in her wake, had long since vanished from the depths of Tartarus. 

Then she pulled the tiara close to her chest, and broke.