logician

I don't think she died then, she merely lost her consciousness. She (JBY) was clearly controlling the ice-stone after that moment, so that confirms her soul was active at that point.

I am 100% certain that Mudoek is the ice-stone (a part or a whole) because:
* Mudoek has control over alchemy of souls (she intervened in Naksu and Uk's soul shifting).
* Naksu's soul is not going wild. It was mentioned that only icestone could do that.
* The relic room's door opened for Mudoek and the relics also mentioned that she is the icestone.
* Mudoek has blue eyes.

It's not clear to me if Mudoek really had its own soul before Naksu entered it. For all we know, the blindfolded Mudoek could actually be just a manifestation of ice-stone and not a "soul" in itself.

After reading the comments here, I decided not to watch the last episode and just assumed that the 15th one is the last episode. So I did really enjoy this drama, especially Choi Go's character, and also satisfied with the assumed ending :)

Yeah, even I was dumbfounded by the above turn of events. But one point to also consider is that, as I have heard, Korean society puts a lot of pressure on ppl to go into top universities (SKY) and work at large organizations (Samsung, Hyundai etc.) Don't know if it's really completely true or not, but so much societal pressure can negatively affect ppl like this.