With a druid and a blood mage in the group I am going to GM it that it's fairly common. They are way too dangerous without enough counterweights.
By counterweights I am guessing that you mean that the PCs need to encounter other magic users as a means of providing challenge in encounters? I would agree with that. I wouldn't want to say that magic is rare and there by limit the tools at my disposal as a GM. Magic exists and should be utilized. I am more just curious about others thoughts on what magic exists where and is who is often wielding it.
Stone singing is an art and a craft among dwarves and those who command it have great respect. Other kin probably think it's wierd but somewhat intimidating.
Outside of Dwarven strongholds how would you envision say a human or Goblin coming to learn this ability? Would it be more likely that these kin would have some close relationship with Dwarves and had the chance to learn through trade? Or could a frailer, seeming to have innate magical prowess, witness stonesinging and teach themselves through trial and error?
My initial thought on how to build a stonesinger who isn't a Dwarf... Say they are a human who toiled in fields that were near mountains. Throughout their life they would constantly need to pull large stones from the earth when readying the land for planting. They always respected the stones and maybe carved them into depictions of the god Huge (I think that's the dwarfy one). Maybe through some accident or otherwise they manifested the abilities of an initiate stonesinger, possibly from divine intervention or something. Proximity to Dwarves or at least mountains seems paramount to me.
Necromancy, demonology and taming of elements that have been twisted from godly intentions and laws of nature were developed by frailers – half elves raised in human culture. They also learned the basics from elves, but have no moral or cultural restrictions.
Is it widely known that Zygofer (sp?) was/is a frailer? How much blame would other frailers carry just for being the same kin as the person responsible for bringing the Blood Mist to the Ravenlands?