Trapped in Mount Penance

Flash Magnus has been the mentor of his descendant Flash Sentry for a long time since he helped quell off Magmatacus before his return. However, the two end up missing as it's revealed that they're trapped in the underground penal catacombs of Mount Penance, as they were framed for a wildly-offensive crime against the Wild Dragons, as Ember and her friends believe them to be innocent. Thus, with the focal points unable to be triggered again for another hundred years, the heroes must go knee-deep into the center of the Earth to discover the true culprit. It's discovered that it's a dragon named Brimm (If you feel he still shouldn't be in the series, feel free to change to name to something similar), who is hateful of ponies because of, shock of all shock, Pred Judu Des, who slayed his entire family, and thus has a prejudice against all ponies, and is searching for a way to escape Mount Penance now that he has gotten rid of the force that beat Magmatacus, a dragon he looked up to, so he can instill destruction upon Equestria. Will our heroes save the day?