They don't gotta put up with aaaaaaaaany water-folk in their life.
We are fortunate then that we are based in Laurelorn, where there aren't any water folk then, are we not? As per word of Boney, those elves that Cython is familiar with are Ultuani and Druchii sailors, and during recruitment we can honestly say that the Laurelorn forest-folk are better enough to be bearable.
And with any Ultuani elves, even if we'll recruit them (and that's a big if, I'm not sure Thorek will all be ok with that), we can deal on a case-by-case basis, it's quite easy to argue that this particular individual is not bad enough to be not in conflict with.
Appealing to curiosity? Cython lives in a huge Waystone nexus, was able to detect it waking up, and has shown exactly zero interest in it. Waystones just don't seem to be an interesting topic to Cython.
...
Using the Gambler? The coin twists probability, and makes favourable outcomes more likely. It doesn't outright create those outcomes from nothing- it needs something to work with, and with Cython there really isn't. The best it could probably do is ensure that Cython is in a good mood when we approach them, which wouldn't be anywhere near enough to let us bring them on board.
We can use that, with additional influence from interpersonal interaction. Cython likes interacting with Mathilde on its current puzzle enough that it regularly initiates these interactions, and this makes it possible to propose to it considering another puzzle we are currently wracking our brains with, hopefully enticing its curiosity and initiating joint discussion on our puzzle.
Reciprocation to a pleasant neighbour, we listened to its puzzle and jointly thought about it, now we'll listen to Mathilde puzzle and jointly think about it. And that's an opening the Coin can use, and use it to get a favourable outcome, because part of the thinking about puzzles is gathering relevant info, like we did from books on dwarf Ancestor Gods, and some of the relevant info on Mathilde's puzzle can be gotten only from some other people gathering in that other place, and so on. And this is not a proposal to try to dupe Cython, honesty all the way, just showing things in the favourable light.
I'm not saying that it's a certainty, but I honestly don't understand how it can be stated that it's impossible and there is no chance.
@Boney, could you clarify any of the following?
Is using "[ ] Attempt to bring a non-Order magical tradition into the Waystone Project (specify which)" action to attempt recruiting Cython, as you ok'd, has a chance of success and is not an impossibility? I'm assuming that it would, because I don't see a point of giving the quest players an option for an action which can only fail, but maybe I'm missing something?
If the action has a chance of success, is taken and is successful, would it take care of any logistical issues, like accomodating Cython presence with relevant Laurelorn authorities for times when Cython will be present on-site, or would there be a requirement for additional actions for possible additional issues? I'm assuming, like with Thorek, that the successful recruiting action would also take care of anything related like that; am I mistaken? Or is it try it and find out situation?