First Encounters

Long ago, Sviagrin, then but a wee new outpost established to survey the geology of the Pilosus Mountain, was in the midst of a dire crisis. It all began with just some strange rumblings in the night. At first, everyone believed it to be nothing more than the regular volcanic activity that the Iron Peaks were no strangers to, and they all simply shrugged it off when their resident geomancer informed them that he found no geysers or magma pools in the vicinity. A few cats had gone missing here and there, but that was easy enough to chalk up to the handiwork of an "overzealous" butcher. It was not until an entire pack yak vanished without a trace that the sheriff grew suspicious enough to come burst down the butcher's door to start asking questions, but there were no signs of slaughter for anything except a few wild geese and rabbits that the hunter had brought in along with one delectable donkey that the expedition leader had held a deep-rooted grudge against.
It appeared that the dwarves of Sviagrin had a mystery on their hands, but before the good people could even go about formulating a plan to solve it, that very night the whole outpost shaked and quaked like never before, and then there came frantic screams from the potter's workshop. The other residents all rushed over, half-expecting to just the grown dwarf bawling his eyes out as he was scooping handfuls of shards of broken chinaware; however, when they arrived on the scene, there was indeed plenty of fine china laid to waste, but the potter was nowhere to be found. More worrying still was the scattered blood splatters, indicating there had been some kind of struggle, along with tufts of black and brown scraggly fur littering the area, betraying the presence of an unknown dark assailant upon the outpost of brunette mountain dwarves.  
Upon inspecting the area, the sheriff noticed that there was one piece of evidence that gave them a solid lead on the nature of the attack, and that was that there was one large section on the workshop's wall where the engravings were in disarray, almost like a puzzle with the pieces put together in the wrong places. Similarly, on the smooth stone floor, there was a rugged patch roughly the same size as the section on the wall where the ground appeared to have been hastily displaced and then cobbled back together. Whatever the monster that did this was, it was something that could easily burrow through the solid stone floors and walls of their mountainhome. 
A wave of panic beset the outpost as they then became besieged by the mysterious rumblings from down below each and every nightfall. The whole outpost shook as Dwarves too afraid to be alone in their beds gathered together in the dining hall, sleeping on the stone benches and using plump helmets for pillows; frantic chickens abandoned their roosts, clinging to the roots on the ceiling with their talons and hanging up there like bats; the other donkey rolled himself up in yak dung to ensure that no beast or dwarf would dare devour him as had happened to his brother. Everything was in chaos, and one by one the creatures of the outpost were disappearing into the dark, shuddering nights. Finally, the expedition leader put his foot down and declared no more. He issued every able-bodied dwarf a pick and ordered them to dig straight down until they found the source of the abominable rumbling. 
And so the dwarves dug and dug day and night in hopes of finding the sinister source of the disturbance. Down and down they went, ever deeper beneath the depths of the Pilosus Mountain. The brave dwarves became greeted by the tremors earlier and earlier each night, letting them know that they were getting closer to the nest of the shuddering menace. Then one twilit hour, they could hear the rumbling somewhere just to the right of their tunnel, getting orders of magnitude louder with each passing second. Without fear, they changed the course of their digging directly towards the noise, charging forward through the wall of stone and earth between them. Finally, there was a loud clang of steel against steel as just as one of the miners struck into the dirt, something on the other side struck back. The wall of stone and earth crumbled before them to reveal a sight these dwarves had never before seen. In front of them was a group of short, stout, stocky dwarves with skin as pale as marble donning craggled obsidian beards. In their haste and frenzy, the dwarves of Sviagrin charged forward, immediately assuming that these darkened dwarves may have been the source of the black fur. Steel clashed against steel and mountain dwarf clashed against deep dwarf as the two groups beat the ever-living daylights out of one another. 
Suddenly, the earthen walls began to quake and rumble once more. All dwarves turned their attention away from the fight, perhaps after throwing in just one more punch or two, and watched as the wall of the tunnel crumbled. Just then, there burst forth a massive black-and-brown haired, furry-and-ferocious beast with pickaxe-sized, razor-sharp claws and a nose with tendrils the size of octopus tentacles: the dreaded dire mole. The dire beast roared with fury, and so too did the dwarves as they rushed in as a united force. Blood was spilled and lives were lost, but at last, after the long and brutal battle, a pyrrhic victory was won.
While the mountain dwarves and the deep dwarves did not share a common tongue, eventually they managed to work out the misunderstanding between one another. It turns out the beasty was besieging the deep dwarf outpost of Underhelm every morning, and so they had had enough and were going up on their own journey for vengeance just as the dwarves of Sviagrin were going down for theirs. The dwarves all had a good laugh and shook hands over the corpses of their fallen comrades, and from that day on they all became the best of lads.