In the Crystal Wars timeline, when Celestia's prized student is captured after a failed skirmish, the princess tasks some of the Wonderbolts and a small team of ground pounders with her rescue. Under Lieutenant Rainbow Dash's suggestion, the Pie sisters are brought in for support.
As formidable a group as they make, they must travel deep into Sombra controlled territory. The trials they will face will test them, but success will grant the beleaguered EUP the hope they've long since lost sight of.