"Derpy!" Rainbow Dash slammed Derpy's nuclear bunker door open hard enough to generate a draft in the room.
Whoops, that's actually the nuclear blast behind her. Better close that quick!
After slamming the door shut again and miraculously not getting incinerated, Rainbow Dash rushed to Derpy, who was currently furiously typing away on her self-built supercomputer.
"Derpy!" Rainbow shouted again, catching the second mare's attention, "You gotta help me! Twilight has no idea what's happening anymore, but I do! It turns out that the planet has an outer shell of highly volatile radioactive isotopes that Celestia manipulates with her magic to form a pseudo-sun burning with the power of not nuclear fusion, but fission! And now that the Royal Sisters have stepped down, there is nothing supporting this outer shell anymore! We need to build a device that can output an immense outward pressure to stabilize the atmosphere while the shell rains down, or we're toast!"
"Already on it." Derpy continued typing. She stopped not long later, slamming her hoof into a big red button beside her keyboard.
Faraway, a machine studded with leaded glass faux-gemstones emerged from the ground. One-by-one, each stone began to glow a brilliant white. Within seconds, the first ring of stones had fully charged. After a minute, three more.
Finally, the fifth ring completed, and a solid beam of harvested mana shot into the sky.
"It's working!" Rainbow gasped as she watched the rolling clouds of debris begin to fall upwards. "Derpy, it's working, you absolute madmare! You knew that the particles could be artificially bound to raw mana, didn't you? But... where did you get so much magic?"
Her eyes followed Derpy's pointing hoof to a corner of the room. In it lay three fragments of what was once a whole crystal.