Dumbledore doesn't reverse the trap he laid on the Mirror in time. The Mirror traps Harry and Voldemort outside of Time... and inside the MLP universe. MLPxHPMoR Crossover.
[Poetry] In a land with no heroes, two goddesses seek to defeat the tyrant known as Tirek who has been stealing the magic of ponykind. Only there is no glory as their broken sorority hangs in the balance of a war-ravaged land.