For the most part, citizens of Arx tend to be far less superstitious than one would think of a pseudo-medieval society. This can be partly attributed to the work of the scholars of Vellichor, but there's also a bone-deep inclination to dismiss most reports of the fantastic, even when there's relatively strong evidence to support it... or to quickly forget shocking incidents that occur. For example, while King Alaric IV married Symonesse, a Nox'alfar, most believe the Nox'alfar to simply be another Abandoned tribe. The fact she can't come out in the daylight helps a bit, though.
Question: Does berserking exist and if so, what cultures would exhibit it, and how would it be looked upon by the various houses?
Answer: Yes, there are examples in all the cultures of Arvum, but it is mostly associated with the Northlands and the Northern Bloodrage. Rathlander's writeup in the Hall of Heroes is a prototypical example of that, and it is seen universally (even in the North) as a terrifying condition, with most houses feeling anyone prone to berserker rages as completely unfit to serve militarily. This is largely because berserkers in rages tend to kill allies as well, making it at best a stigma, and outside the Northlands is usually seen as grounds for expulsion.
Question: Q: When did the superstition start? What exactly about them makes people nervous? What's the history behind all that STUFF?
Answer: That's one of those traditions that seems like it has always been there. There's a lot of folk stories about 'be careful of a demon from behind the mirror watching you' or something stealing a person's reflection and running amuck with it. Most of those stories have fallen out of fashion in the past couple hundred years for some strange reason, along with any particular theological teaching about reflections and how they relate to the soul.
Question: With mirrors being a matter of superstition, do Arvani tend to use other media or are reflections in general a part of that superstition? For example, are most people fine with seeing their face in the surface of a pool of water or polished metals, or are those also considered 'mirrors' and thus subject to that superstition?
Answer: Generally speaking, any reflective surface is seen as a sign of the other world, but it's a 'light' superstition, in so much that most laugh it off. Still, some nobility just don't own any mirrors, and it's largely assumed that the tradition of servants helping prepare lords and ladies for formal events came from nobility unwilling to look at reflective surfaces to see their own appearance. Think of mirrors as being considered very slightly gothic or edgy by the populace, and someone that fills their home with mirrors is probably trying too hard.
Question: Q: So the battle at Setarco had an army of monsters, and there were a lot of soldiers there from different fealties of The Compact. So I'm curious how that has effected the natural skeptical nature of Compact citizens. Are the belief in monsters more wide spread? Are soldiers of The Compact treated as insane? Or did soldiers in that battle write off all the monsters as just trained, inbred and deformed animals?
Answer: A: Initially, very little of the first, and mostly the third with a little bit of the second. Most citizens of the Compact scoffed at the wild, obvious vainglorious stories attempting to describe some poor large dogs of war as monsters, and are indignant that veterans of the battle would insult their intelligence by trying to claim that 'monsters' were there (but thank you for your service, btw). A great many soldiers change their stories after the fact, saying they found things they couldn't really explain, but don't want anyone to think of themselves as crazy.
However, in very recent weeks, there's been much less pushback against it. Something might be changing.