The flesh on Starlight’s legs was starting to slough off. Desperately, Twilight tried, again, to break the magical barrier Starlight had placed around the entropic field she was generating. It didn’t work. 

“You have to do something, Twilight!” Trixie wailed, as if Twilight had not been trying to do things ever since Trixie had come to her and told her the situation. “You’re supposed to be the [i]special[/i] one, the alicorn princess! You need to save her!”

“I’m trying, I’m trying!”

Sunburst found another spell. “Look at this one, Twilight! It [i]crystallizes[/i] entropy.”

Quickly Twilight read through it, and sagged with disappointment. “I’d need to be a dragon, Sunburst. This wouldn’t work from a pony’s horn.”

“Ah, well, [i]there’s[/i] a thing I can do!” Discord said, his face lighting up. He’d taken it very hard that Starlight had woven the protective barrier at tolerances that chaos could not match or overpower, like a weave so tight even a sword couldn’t cut it. 

“No, Dis-“ He snapped, and Twilight was an adolescent dragon. “-cord! Put me back, I don’t know [i]how[/i] to cast magic as a dragon and I don’t have time to learn!”
Starlight was laying down now, her legs skeletonized. Her face was starting to sag with rapid aging. Her own horn flashed as she tried spell after spell to get the entropic field under control.

 “I don’t think she can hear us,” Fluttershy said softly. “When I put my ear to the barrier, I hear a loud roaring.”

Discord nodded somberly. “Accelerated entropy does that.”

“Can you maybe send her a scroll?” Sunburst asked Discord. 

“I can try,” Discord said, and the scroll vanished. It appeared in front of Starlight for a moment and then fell to pieces.

A flash of teleportation lit up the room, and Celestia and Luna appeared. “Oh, no,” Celestia said. “I know what she’s trying to do.”

“What is she trying to do?” Twilight asked.

“If she masters entropy, she can heal, and prevent death. But it’s impossible. I had to watch three students dissolve like this, Twilight. I’m so sorry.”

“No! I can see what she’s trying to cast and I think it [i]could[/i] work, but it doesn’t have enough power, and her magic is getting weaker. Discord! If you can transfer me some of your magic, maybe I can break the barrier, and then transfer it to her!”

“You’re that adept with chaos now?” Discord raised an eyebrow. “Well, let’s give it a shot!”

Power, twisted upside-down churning power that made her mildly nauseous, slammed into Twilight’s horn. The world went white. She channeled it into a laser pinpoint against the barrier.

It cracked. Starlight lifted her head. Her horn glowed with the transfer, and the barrier filled with brilliant light.

For a moment, Starlight smiled, and then she crumbled to dust.

The barrier fell. [i] “No!” [/i] Twilight wailed. “No, no, [i]no! [/i]”

Celestia’s ears pricked up. “Excuse me,” she said, and vanished.

Twilight stared at where she had been. [i]Excuse me? [/i] 

“Hold your tears, Twilight, Trixie,” Luna said. “I believe they are misplaced.”

“[i]Misplaced? [/i] Trixie’s best friend has just [i]rotted[/i] to nothing and—”

Teleportation light filled the room again. Celestia was back… with Starlight. Who was taller, and had wings.

“I’m sorry I worried everyone,” Starlight said. “And thank you, Twilight, I’m not sure I’d have been able to get it without that last boost you gave me.”

“You [i]idiot! [/i]” Sunburst swept her up in a hug. “Never, never try a new spell without involving me, ever again!”

“I don’t understand,” Twilight said. “How--?”

“When you create new magic in the domain that you are destined to govern, that is what makes you an alicorn,” Celestia said. “But I thought it would be Time, Starlight.”

Starlight shook her head. “Time’s too risky. Been there, done that. Trying to control entropy only risked me.” 

“Does this mean you can end death?” Fluttershy whispered. 

“Even an alicorn’s not that powerful,” Starlight said.. “But I can make sure nothing dies before its natural time runs out… and I can extend life.”  She looked at Twilight. “I did it for you, Twilight. I was so scared of what would happen to you if you live on for thousands of years, but your friends all die, and your brother, and who knows what would happen to Cadance and Flurry then? But now we can all be together, for as long as we all desire.”