When Sui Xiong was saving the great drought that had engulfed the entire main-plane continent, he had also produced a great deal of salt along the way—truly a great deal, enough to pile into a mountain.
Of course, it was all crude salt, bitter and astringent. Poor families might not mind the taste, but Sui Xiong himself utterly despised it. In his eyes, this sort of salt was garbage. Not only did it taste bad, it also contained large quantities of minerals harmful to the human body—no matter how lacking Sui Xiong was in scientific knowledge, he knew seawater could not be drunk. The key reason was not that it was dirty, but that it contained large amounts of harmful minerals.
Sui Xiong had once heard a piece of popular science saying that seawater was undrinkable partly because of its excessive salt content, and partly because of the various other minerals it contained. He did not remember exactly what those minerals were, but he still remembered some of their names—vomiting salt, purging salt... You could tell what would happen if you ate them just from their names.
Thus, although he had acquired mountains of salt while obtaining fresh water from seawater for disaster relief, he had never found a good way to use it. In the end, he assigned Palin, the chief research expert of the Church of Void Mask, a project: to study a method of purifying this crude salt into edible salt.
This world also possessed salt-drying technology, and naturally had methods to turn crude salt containing a large amount of impurities into refined salt that was nearly impurity-free. But all those methods required magical assistance and were far too costly. Aside from supplying the upper classes with luxuries, they had little practical value.
The specialized spell "Purify