Kiplyn leaves behind his shield and backpack, taking only his dagger and possibly 1 or 2 other small items of his choice. The tunnel is so low and narrow that he can't even crawl; he has to wriggle on his belly like a snake. In order for his shoulders not to get stuck, he has to stick one arm out in front of him (like Superman). He soon realizes that the light from his friends is mostly blocked by his own body, and he's basically slithering blind into the darkness.
10, 20, 30 feet, and then the other Hobbets can no longer see Kiplyn; he is beyond the range of their lantern light.
The tunnel curves gradually to the right, and soon
Kip realizes that he is completely turned around, a full 180 degrees from his starting point, and the tunnel is spiralling in on itself. To make matters worse, he feels like the ceiling and walls are closing in on him. It's subtle, barely perceptible, probably just his imagination? He stops for a moment to catch his breath and fight off the rising tide of claustrophobia. There there, everything is going to be okay. Deep breath.
As
Kiplyn's eyes adjust to the darkness, he becomes aware of a faint greenish light from up ahead, just around the next bend to the right. It's a faint, sickly glow that does not flicker like flame.
Every layer of
Kiplyn's civilized, surface-world programming is
screaming at him to turn back. And yet, he feels no threat, no sense of danger. The tunnel is the perfect size, as though it were made for him, zero risk of getting stuck. There is no physical challenge ahead; the only barrier is in Kip's mind. He feels, if he were to continue around the bend, toward the greenish light, it would awaken something in his lizard brain, a primal burrowing instinct that lies dormant in every Hobbet.
Going forward requires a SAN check. Since Kiplyn's current MYTHOS is zero, he would automatically fail that check, and his MYTHOS would increase to 1. Do you accept the consequences? Will you continue on toward the green light?