The players travel to Civilia, where they are met by a harassed administrator called Uncertain Passage, who sends them off to deal with a cave-in and murmurs of possible creatures in the city's silica mine.
As they go, they see evidence of some civil unrest in the streets (punch-ups in people's houses, people not working who should be working, etc) but no revolt. Something is clearly a little wrong in the city.
When they get to the mine, the overseer Elevated Engine explains that, even prior to the cave-in, miners had been getting superstitious about an ominous rumbling that they had heard from deep within the mine, and the miners believe the cave-in has something to do with this and are scared of what may be behind the rubble.
Elevated Engine gives them a basic map of the mine and its seven levels of tunnels, a large drilling machine with which to bypass the cave-in, plus a couple of hard hats, and wishes them good luck. Meanwhile, many small cave slugs around the mouth of the mine are annoying.
The party are successful in drilling around the cave-in on the second level, despite the best efforts of many falling rocks to damage the driller. On the other side, a large family of slugs are very upset that their nice empty cave has been invaded by people again, but they are dealt with reasonably quickly.
The party investigate the tunnel and the caved in rocks, and realise that something has been causing the rocks to become less structurally sound - something burrowing through them in tiny tunnels, leaving them honeycombed with holes. It looks like this is what happened to the part of the tunnel which caved in. While investigating this further, and seeing that many of the tiny boreholes seem to be emanating from a point down below, the party also hear the ominous rumbling from deep within the mine. They continue downwards.
On the fifth level, they encounter a large number of Burrowing Mites (both large and small), who appear to be fleeing from something further down in the mine. Not fleeing so hard that they can't fight adventurers on the way though.
When they reach the seventh level, lowest portion of the mine, they see more tiny mites attempting to flee out of a particular section of wall which then starts to glow, before slumping into lava and revealing an extremely strange, huge burrowing, worm-like creature, which is clearly the source of the ominous rumbling sounds. The creature appears to melt rock, consume it and then excrete it (in slightly aerated, ashy form). It is coated in diamond plating, except at the rear where it seems to be softer, graphite-like material, and it travels . The creature does not target the party and they consider just leaving it to its own devices, but then it accidentally splits them up and they are forced to fight it. Stellar Glory learns that its graphite rear can be damaged, while Manifold Ghosts is stuck at the front of the diamond maw which is impervious to damage (and spits lava, but luckily Manifold Ghosts is impervious to that). Bored of this, Manifold Ghosts decides to lean harder on the fire-imperviousness and climb inside the maw, where diamond teeth strike them while they seek out softer areas to strike back. Just as they find areas further back in the digestive system which can be damaged, Stellar Glory manages to destroy the rear of the creature, and soon it is killed.
While inside the creature, the communicator that Manifold Ghosts was carrying got a bit melted. They attempt to fix it, and fix it inside themselves, but end up making it an always-on transmitter and receiver (receiving specifically the extremely Civilia-patriotic local radio station).
Recovering from that exciting experience, the party - who are both extremely strong - strip the monster for as much diamond plating as they can carry (6 plates, 60% of what the creature was covered with) and leave the rest for the miners to recover.
Dealing with one more slug fight, the party are able to return to the surface and report to Elevated Engine what has happened, plus their belief that the mites, in their terror to flee from the diamond borer, were causing the cave-in problem and that this has now therefore been resolved.
Elevated Engine and other civilians present are overjoyed to hear this, and in their discussion it becomes clear that the real problem with Civilia, and the reason this mine is so important, is that the silica mined here has been used to make glass lamp globes, which ever since the events of
Culture Methods over a year previously have been the main way of getting the ship heart
Civilia to help keep the city running smoothly. The locals also comment how much
Civilia will love the diamond plates, and advise the party not to let
Civilia see any that they don't want to give it.
The party take this advice, but do go to see Civilia after stashing a few diamond plates somewhere safe beforehand (Manifold Ghosts stashes two after handing one over to Elevated Engine, Stellar Glory stashes one). They pay appropriate verbal homage to Civilia and hand over one diamond plate each, as well as sharing as much information about the creature as seems sensible. Civilia is indeed fascinated by the idea of getting more diamond to make chandeliers etc with, and promptly demands from its administrators the creation of a new Adventurers' Guild which can go and hunt down more of these creatures.