[Thank you, but this idea I had was only turned into a proper story by the people who took it upon themselves to venture out in search of the truth. So again thanks to all the participants in the search and my special thanks to LigH for the great documentation. Just to wrap things, here are the two fragments that I though up as basis for the story.]
Letter to Aunty Carpia (as found in the Gobble village at the river)

The remnants of Troutmouth Kelpslinger's diary (as found near his body in the tunnel)

[As I would like to thank every individual player for their participation, and the actual "prize" laid out was made up of too few items for such a large group, there will be a "Diamond of Waterkin" for every participant. I will list the names here and tick them to keep track of who I managed to give their individual rewards:
- Cirerey
- Derator ✔
- Dalos ✔
- Eisenhand ✔
- Esanor ✔
- Gonger ✔
- Kaerli ✔
- Laros ✔
- Lumi
- Mrae ✔
- Qiner
- Roled ✔
- Xola ✔
In case you name is missing here, please drop me a line, here or in game.]