So, do you know anything about the Lauke's Followers? I'm sure as an adventurer, you must have heard them a number of times. The group goes back over 50 years, and there are two sects within the group. I've heard that it's some mysterious religious group...
Incidentally, Via Marea's attempting to open up communications with them as the nation's existence depended on it. I'm sure there is some vital reason for this, but we shouldn't rack our brains trying to figure that out.
It's a decision the queen made, and we just follow her orders. All we need to do is bring 5 Rainbow Trout to the queen.
You can get to the fishing grounds by talking to the Fishing Hole Gatekeepers stationed in every capital. You can buy the Rainbow Trout if you can find anyone that sells it, but you'll have better chances catching them yourself.
Take 5 of them to the queen. Now do you see why I told you that you'd need luck on your side? It'll be one of those rare tasks that you'll enjoy. Good luck. Hahaha.