After a lot of reflection, here is what I think the story of Salt. This is just my opinion, and I am open to criticism, and there are still some holes in my theory. First, we have to start with Frostfound, and with the sun. A long time ago, in the majesty of the High Wilderness (Sapphire Chamber), monstrous being lived, which included the Sun and his Courier.(Amethyst Gallery) The Sun and his Courier betrayed the laws of the universe, and committed a terrible deed, which violated the laws of the universe: they had a child. (Cavity) This could not do, and so they hided their their child in secret so no one could find it out. (Emerald Vista) Now enter the White, the spymaster of the Judgment. I don’t know if he knew that the child existed, but he knew that something was up. So he sent an agent into the Neath, Salt. (The Diamond Bridge) To enter the Neat, Salt had to give a part of himself (The Iridescence) and entered into the Neath (The Dark Room) Salt created Kingeater’s Castle, and find out that the child was here, but they couldn’t find a way to get to her (Need), and so they started a correspondence (not the language) with her. Her name was Stone, and the correspondence between the two of them calmed Salt’s need. (Distant acquaintance)
My theory is that the White forced Salt to need to find Stone at all coast, hence their hunger, but talking with Stone tempered their hunger a bit. (They also tried to talk with Stone, but that went nowhere.) Slowly but surely, Salt started to like Stone, I would go so far as to say that Salt was in love with her. (There is this beautiful line in the « Distent acquaintance » which says: « […] when the time came for the monarch to depart, the monarch’s appetite was transformed, like blood into tears. ») Which is then they realised how awful the White’s plan was, how despicable the White can be, and how crushed the Sun would be by her daughter’s death. But they could not stay in the Neath, for their hunger was too much to bear. Instead, Salt had an idea.
So, they hatched a plan. They removed all of their memories, and created Frostfound. I do not know what was East at the time, or if the Deconstruction was there, but suffice to say, it decided to go East, and hid the way to get there in Irem (Salt as something to do with Irem, but I can’t find out more.) All that remained of them was the desire to travel, to go forth, a desire they broadcast everywhere into the Neath, so that they may find sympathetic souls who might learn their story, and joined them East, to grow make them more powerful. And one day, they will get back to the White.
There is a lot of thing missing in my theory, like the link between Axile and Salt, but that’s what I have for now. Oh, and if you want to reconcile the apocryphal motivations of the White with my theory, here is how I think it goes: The reason the White wanted to find Stone was that she could be killed, and therefore the Sun might end its life. With this, he could elaborate the council of peace, a message that went sent would make every Judgment that hears it kill themselves, and also ending the universe. This would be different from the Liberation, because the Liberationist don’t just want the absence of light, but the presence of darkness.
Also, I think, if my theory is correct, it explain the "heart is destiny’s engine" line. By becoming a being of desire, by inspiring people to travel, this allow Salt’s plan to come to fruition (also, it think this sentence resumes Fallen London’s theme). Finally, why do I think Salt fell in love with Stone? Well, Stone is the Bazaar’s child, and "In matter of the Bazaar, look to love, always. »