Another fifteen minutes later, the bottom comes into view. It's not shimmery or layered like heartmetal is or the walls were, which is somewhat surprising. Instead it's a strange, indistinct gray surface with things moving all over it. No time to look further, though, it's time to jump onto the last level of side shafts. You pull the two-step with the elevator side platform, and almost get hurtled ahead down to the bottom level of passages. A quick step off, and you're in a groove running three-quarters around the edge of the huge pit. You can make out the tiny circle marking the top, far above, and the slashes of the funicular tracks, but there's little else to mark your passage.
With your gear at the ready, you begin exploring the side passages. Sessh doesn't hear anything, Uncle is ready to hide like usual, so you creep through the tunnels, glowstones out. The shadows are dim, but this isn't a proper dungeon. People dug these tunnels, not the raw forces of creation. They're uneven, the floor isn't rough, and the walls are pitted and cracked.
"Huh, there's mithril here", says Sessha, leading the way, talking about a shiny spot in the wall. "They were really dedicated to the heartmetal, weren't they?"
"Should we dig it out then? Should be worth it."
"Lets remember it for the way back. There might be some reason for leaving it alone. If we've got time, we'll certainly fill our pockets."
The next area is a series of cracked blocks, rough on the ground. There's a thin middle path that's been smoothed out, but it's too smooth to be safe. Sessha barely avoids slipping, and the rest of you climb slowly down the cracked blocks. The path splits, and splits again, Sessha getting out some chalk to mark the walls with the way in and out.
As for heartmetal itself, you don't see any. Uncle suspects that whatever the 'extraction' process is, it might involve dissolving the heartmetal, as there are plenty of pits in the walls and even the ceilings. There are even some in the floor, although the central path remains open. Three or four times you pass precious metals or resources in the mine, keeping track of them for later.
Eventually you find that this mine passage broke into a natural fissure, running over a hundred feet down and at least a hundred feet up. It's a good twenty feet across. On the other side you can make out a few natural caverns of various size that may well have more valuables.
Do you cross? And if so, how? There are more tunnels on this side to explore, but this fissure stopped the robots.