Page 1261 — Cracking the Shell
Generally, as a DM, when your players ask "So what would've happened if…" it's best not to answer. There are several good reasons for this — it helps you save that content for another time, and it keeps the mystery of the locations you build alive, keeping them interesting. But when it comes to potentially boundary-crossing stuff that inadvertently comes up in the session, full disclosure and reassurance is usually best.
Transcript:Gallus (RD): <roll> Aha, got it! Finally!
DM: You did it?
Gallus (RD): This'll put me up to seven successes, on attempt… 29.
DM: Ooh. My math might've been too precise…
Gallus (RD): Well, that "canceling each other out" thing didn't help!
DM: True. At any rate, congratulations! The layers of overlapping crystal have expanded just enough to create a hole that you can climb out of.
Gallus (RD): Hooooh, thank goodness!
DM: Outside is the catacomb passages, not too far from the entrance, in fact.
Gallus (RD): I climb out.
DM: You climb out!
Gallus (RD): Out of, uh, morbid curiosity, what would've happened if I'd… "failed?"
DM: Well, at 30 attempts, you would have run out of beams for a while until the light changed. At net six failures, it would've gotten so tight that you would hardly be able to move, and you would've had to wait for someone to dig you out from outside.
Gallus (RD): So I wasn't actually gonna be crushed?
DM: Well… you're playing a kid. I gotta pull my punches a little bit.