In the wake of Discord’s flippant betrayal in the fight against Tirek, Fluttershy falls apart. She doesn’t answer the letters Discord sends her, sequestering herself in her cottage until Twilight and Rainbow Dash nearly force their way in to help her put her life back together.
Discord, meanwhile, is swallowed by a feeling that cuts much deeper than simple selfish grief. To ensure that Fluttershy is never harmed again, he flees Canterlot and finds himself using unconventional magic he swore he’d never use, filled with a purpose he’s wholly unfamiliar with. Things quickly get out of paw, claw, and hoof.