@Tribes
Thorn brings up a thought-provoking point. We should be careful.
However, I would say that:
* Whatever this thing does, it may not be just an explosive blast. It could spread poison gas, or lots of little baby monster worms, or, more likely, huge quantities of the same acid it spewed at us. In all those cases, having it down in the hole is best.
* Even if it is just a big explosion, being in a confined space will not in any way increase the force of the blast, it will only channel it. That does suck if you are in the channel, but the channel will be straight up - blast force does not turn corners. The overpressure can also suck if the vessel is something easily shattered, like a porcelain toilet. In this case, there will at least be several meters of decades-old lava flow, and possibly some igneous bedrock below that, depending on depth. The only way an underground detonation could bite us in the butt would be if
(A) there was untapped natural gas (which I think would have been exploited by now, and if it is down there would likely ignite even with a surface explosion.
OR
(B) if the blast was strong enough to cause a geological event, like split the ground out from under our feet or something - but if the blast is
that strong, we would still rather have several meters of rock between us and it, than have our bodies and the fuel cell be directly exposed to it.
But I'm not a physicist or a geologist. As usual, Al knows more about this than I do.
He's got nine dice for Mining knowledge, and nine dice for Demolitions, and even nine dice for Puyallup Barrens (for underground hazards???).
So I'll make a single nine-dice test as an amalgam of those, to see what Al thinks he ought to do.
Since ultimately, all that really matters is what the GM thinks!
So just assuming we are talking about a vanilla explosion, best underground or on the surface - opinion based on Mining and Demolition.
Blended Demolitions/Mining roll:
9d6t5 3All assuming we even CAN get the thing back down in its hole!!!