The dream was (as Wishbone relayed it, anyway) cryptic. A large eye, blood-red and flaked with gold, surrounded by a gear. It loomed down on Wishbone as if it could see him, and the ground swallowed him up. He claimed that while in the ground, he saw entire oceans of numbers, and somehow knew that the largest ones meant something important. When he woke up, he scribbled a series of them on a piece of paper; that series happened to correspond to a point on a map, and that point on a map was the cave. "The greatest treasure of all time is here", he said of it. That was enough to convince Tail Gunner, and two-against-one was enough to convince you.
You proceed down the hallway, the silence deafening. For a time, you walk down the hallway, until you come to a junction: a perfect T. As you approach, a piece of wall rolls down into itself, and out pops something that looks like a cross between a spider and a metal sphere. It's small, and it chirps happily as you approach.
Wishbone stretches out his hoof and holds you back. "This thing was there. In the dream. Or something like it. Let me see something. This might be important."
Tail Gunner, however, is having none of it. "How long have you been an adventurer, dude? When something pops out of a hidden door, you kill it. End of story."
The spider-thing doesn't look dangerous. It's about the size of a baseball, too small to conceal any weapons you know of, silvery and with a single blue eye set in the middle. Four spindly legs hold it up from the ground, and it turns about quickly to regard each of you in turn.