How is Mal du Pays different from a normal Sadness?
Mal du Pays is different from a 'normal' Sadness. To start with, they started off as incredibly strong--very strong emotions in a place filled with Craft and the King's Tears. That's why they popped out, fully formed, without any dripping at all.
However, it was feeding off of both Siffrin's and the King's Tears, both of which are just ripe full of Wish Craft. Absorbing that changed it, ever so slightly. It's nowhere near as much of a 'person' as Loop is, because it does not have a core.
But it is definitely much smarter.
The Wish Craft also changed it enough that it lost the ability to communicate with Siffrin. Normal Sadnesses are always able to talk to their creator. But Mal is now completely silent, because it is not 'normal' anymore.
So you have a monster that knows that it needs to feed off of liquids and Craft energy, and knows that its creator is Siffrin, but suddenly can't communicate with him.
Since it's also formed of all of Siffrin's worst tendencies, it is consumed by that crushing touch-hunger and a need to be comforted and accepted.
When Siffrin doesn't immediately try to kill it when it appears a second time, it essentially becomes completely obsessed with them.
It's also smart enough that it sees the party feeding Loop, and decides to try to get some of that for itself, because not only is it a lot of touching for exactly what it wants, but everyone seems to like Loop a lot, particularly afterwards!
Unfortunately it doesn't really understand such things as 'consent' and that backfires splendidly. Now only Siffrin (and sometimes Isabeau, with great trepidation) feed it.
It generally acts like a surly cat who only likes one (1) person, and that person is Siffrin. It likes Loop as well, but after the star!incident Loop only barely tolerates it. It pushes its luck whenever it can, though.
Mal still experiences normal Sadness instincts, though, like splitting when it gets too wet, hiding from light, and a desire to feed from its creator.