"Don't worry, Princess. Let's put it to use right now. What was that spell again?"
"We have no time to teach you the spell. Are you willing to take on the responsibility of holding the shield?"
"I will take the burden off your hooves if it means we can save this planet."
"I need to free up my horn to do this spell. It is a large and difficult one. I can not do both."
"Yes, I understand," she nodded.
Twilight connected herself to the temperature shield and took half of the pain. When Celestia disconnected herself, the rest of the burden hit Twilight, and hard.
As she grunted because of the strain, Celestia began the complex protection spell.
Her horn lit up and zapped the amulet. It floated in place as it became brighter, apparently working. Their confidence grew more as it continued to glow. Until it shattered, and with it, their hearts and hopes.
Celestia bowed her head in somber acceptance.
"What?!" Twilight shouted in distress. "No! It has to work! We . . . We can not fail . . ."
Shortly thereafter, Twilight failed to preserve the temperature bubble as it became too overpowering. With the heat being able to enter Canterlot, everything was immediately scorched. The expansive fireball then engulfed the entire planet.