A Bad Case of the Shake'n'Quakes

The Freed Changelings and Molemen invited the Lougers and the Main 7, along with Thorax's hive, plus Tempest and Grubber, to their first anniversey party of the underground world being freed from the Undergrowth King so long ago, as the Underground has became a better place with Undergrowth King gone. However, the party was cut short by a giant mining sub being manned by a rock golum named Crudder, and a female bat-being named Subterra, basicly the Tempest expie of the latest Storm Clan trouble-maker of the week, The Quake King, who on behalf of the Quake King who will arrived soon in an even bigger underground sub, have ordered the populace to surrender, forsake the holiday celebrating the desicrating defeat of the Undergrowth King, reveiling that the Quake King was the only member of the clan with legit sympathy for Undergrowth, ineditable downfall or otherwsie, or failure to comply will lead to things being more forceful, as Subterra is unpresadently capable of earth magic. With the Strongest Heroes being turned to gold by Midas Orbs, basicly another varient of Obsidian Orbs, even Gazelle barely is when her Uniter Blade carring arm got turned to gold, rendering her harmless to the enemies, what is left is forced to retreat and make a long adventure into the world of the underground as they make new friends, including a sly con artist scorpian-cat with a magicly cursed tail that always speaks what's on his mind to the detriment to his conmen career, underground digger pirates, and even a cute but snarky princess daughter of the queen of a subterrian race of digger ponies capable to stomich eating rocks and moss, known as the Undergrounder Ponies, a tribe once considered a true myth until now. However, the heroes now need these people's help, because the Quake King is not just after mere revenge, but to cause all lands in Equestia to come down to his level by causing a world shattering earthquake that if done wrong will doom both surface and under worlds. While the heroes aim to do this, Tempest tries to sway Subterra, who is after them, to reconsider her siding with Quake as even being as loyal as possable will end in betrayal, espeically since the Quake King is an even BIGGER jerk about that, and that the Quake King is an utter madman for trying this. Can our heroes save both worlds from a mad undergroundian king?