I think that sounds great. Limestone is quite porous, if they were wet from rain and/or blood and heated quickly by magic - exploding rocks makes perfect sense to me.
Or the rapid cooling cloudburst, that makes sense too.
Rock and stone can usually withstand high heat. That's why it's used in fireplaces and chimneys. The mortar is often the weakest part of masonry work. Poorly mixed mortar could fail under high heat. As far as stone goes, they can explode if there is moisture in them when they are heated rapidly...
Attacking the mortar, if there is any, would be the most effective. It is usually much weaker than the rock it holds together. Also attacking the arches (KEYSTONE) would also be more effective than other parts, but likely more difficult.
Rapid heating and cooling (fire then water) can causing...
Usually, based on terrain and size of the river.
I would assume the "source" would be a spring of some kind. A natural location where groundwater finds its way to the surface. Based on the way water tables tend to work, ground water would not, typically, be near the surface on a high mountain...
I would think the biggest challenge facing folk in a mountain stronghold would be a potable water supply. Unless they were high enough that snow was a constant resource that could be melted and purified, a continuous supply could be a challenge. Chances are they would be much to high to make any...
I was a bit worried about it being confusing. Perhaps a new thread would have been best, but there was some good discussion in this one.
I'll take this one since I raised this topic from the dead.
I think formal law would separate shunned behavior from behavior that is simply not...