Sam volunteers. They work quickly and eagerly, motivated by how close you all are to cracking this mechanism. Eventually, after a semisystematic attempt to work methodically through the possible permutations, they find the correct combination. You hear the final clunk, and the final scrape, and the Bull's Horns finally give up their secret.
As the final button is pressed and the final seal is broken, a low, rumbling scrape emanates from the rock face. And then you see it: a narrow crack that fissured the weathered rock is widening. The crack was not natural but man-made.
Large sections of the rock face on either side of the crack start disappearing. They somehow retract into the surrounding rock, revealing a large, worked archway and a tunnel leading deep into the stone.
Slowly, menacingly, the great stone bull opens its mouth, waiting to swallow you and your companions whole.
"What are we waiting for?" Esme asks, taking a few steps forward.
"Stop!" you shout. "It needs time to ventilate. Sealed ancient tunnels often contain really bad air. Toxic. Give it time."
"Fusspot," mutters Esme, a little sulkily, but she does not protest and defers to your greater expertise.
The four of you sit at the entrance and wait, thoughts agitated with acute anticipation of what you may find within.
How are you feeling about this?