Uncle accepts your invitation almost disturbingly fast, after finding out that it's safe down there. Except for some puzzle. He does not have any immediate ideas.
What if the thing down there isn't even a thing we can actually grab and drag back with us? What if it's just like, the cave itself is spooky?
"..It could be an area, yes. But this dark sun stuff is fairly compact. Whatever it is, item or area, it's not that large. I can't say an exact size, but I don't think it's bigger than, say, ten feet by ten feet. And it could be as small as a coin or a button."
Once he suits up, the four drop down again. Uncle insists on going over the built-up area first, digging around and pacing out the distance. You're not sure why, but he'll probably fill you in when you're back above water again.
Then it's time to enter the dome.
This time, when you enter, you're in a magic tent, not walking in an open area. There's a base camp here, with an inventory chest, a toolbox, and a couple storage crates along with a number of hammocks. Outside is a cooking setup and several more tents.. in the jungle. Visible are a number of old stone blocks on the floor, as well as trails, one clearly leading to some ancient temple.
"I remember you telling me about that snake temple, Willis. I've never really explored that part of the world. Does this look like that kind of plance?"
Willis nods.