~~Booo, cheap like shoutout. None for you. (Still gives like)~~
Edit! Jokes, it was jokes. Like that this topic came up finally
Do like the question though. I fully intend to drink some of the liquid to find out, but if I was going to make a super off the wall guess
I think it is a fluid that is light sensitive, like the kind of stuff they use in photography, and the reason why it is dark is because it has been exposed already to light.
I think if you can reverse engineer it, you can use this to help create elyrian photography, and given my Alchemical goal set, plan to figure out it's use either way.
TLDR Send coins to Sun Temple and Send Dark Liquid to Labbe!