A pony expedition ventured 6000 meters deep in search of fuel and rare minerals. However this expedition was ambushed by eldritch horrors big and small, for reasons beyond their understanding. An earth pony was measuring radioactivity close to exit tunnel. The rest of the miners tried to fight the monstrous undead horror emerging from the underground lake but in the process ended up collapsing the rocky roof of the cave. Burrying forever almost everybody. Only the earth pony was able to get back to the surface to explain what happened. Afterwards the earth pony was tasked with helping set up an underground outpost above the collapsed cave, to stand watch in case more monsters like this decided to emerge from where that monstrous horror was spotted. The construction site for the outpost was very dark, just like the rest of the underground, it was surprisingly cold. With tiny propane lakes around, which could be refined into fuel for the outpost. Being a miner, the earth pony felt overshadowed by new peers send as the main labour force.