I've also been wondering about the two storms that collided. They felt natural to Linden, but it's a practical certainty that someone sent them anyway. Findail trying to make Linden claim the ring is a good choice, but Kasreyn could also be at fault. Perhaps they both created one storm each.
I think there was a clear implication that the croyel had told Kasreyn about the white gold and that it was at his reach.
As for the power of the yellow gold, I'm tending towards Earthpower. Gold is a color associated with Earthpower, as is seen for example in the golden gleams in the hurtloam. I think malice didn't shine from Kasreyn's works because of his method, which was far more detached and technological than, say, Drool Rockworm's. He did magic with his mind instead of his heart.
I think the croyel will be major plot point in the Last Chronicles.
I think Linden will make a deal with one to keep her alive despite her having been shot to the heart. We have seen her sliding towards the ends justifying the means mindset already. Linden damned beyond redemption? I wonder how that would work out in the end.
I also think Nom will make a return of some sort, that's a hanging plot thread if I've ever seen one, and yellow gold probably will too.