Long after Marble Pie was incarcerated for life by the forces of Empress Nightmare Moon, Mayor Mare was the first to infiltrate the prison to try and free her, along with all the other captured members of the Resistance. But while she got close to freeing Marble, a few extra-vigilant guards realized something was wrong with the prison's newest staff member, and Mayor Mare was caught.

As with all the others, Mayor Mare's show-trial was brief, and ended as they always did: a sentence of life imprisonment with no possibility of parole. She was then mummified alive with magical bandages that would preserve her body and ensure that she could never be freed or cut loose, and then put in a cell and locked inside.

For the next year, Mayor Mare remained in her cell, trying to adjust to her life sentence. It was difficult; her wrappings, while warm and comfortable, were still mercilessly tight and thick, leaving her barely able to move. Worst of all was seeing the occasional bit of sunlight streaming inside, a reminder of the world beyond the prison, a world she would never experience again. Eventually she sank into melancholy and accepted that this was her life from now on.

The very next day, however, Mayor Mare got a surprise: Anon — the hairless, ape-thing that had been magically teleported to Equestria and joined the Resistance — broke into the prison (somehow losing his shirt in the process), fought his way to the cells, tore open the mayor's cell door, and busted her out. Helplessly wrapped up, all Mayor Mare could do was go along for the ride, yelling in fear as Anon bravely fought his way out.

Eventually, the two managed to get away from the prison, making their way to a remote forest. There, Anon finally took a breather and checked to make sure Mayor Mare was okay. Though shaken, she was unharmed, and very much relieved to be free of that horrid place. They still had a long ways to go before reaching Resistance headquarters (where a barrage of magic spells would try to free Mayor Mare from the magic bandages), the breakout was proof that Nightmare Moon's 'impenetrable' prison could be infiltrated, and that those imprisoned within could be freed… and that hairless ape-things from other dimensions were great at doing so.