A magical drug with no apparent side effects.
Production is unknown. There are a select group that know the recipe and have been producing it for "hundreds of years".
Talon distribute the drug around Cal' Haden.
It was originally believed that the Talon control this. We recently discovered this isn't true. A mysterious woman and her associates produce this in order to "pay the bills" as they have other interests and the Talon must take whatever deal they can get.
These secret producers and the Talon obviously are hostile business partners.
Spoilers Below
Spoilers
Nightshade has been discovered to be Soul Wine. A narcotic from the Hells produced by harvesting people's souls. The younger and more innocent the better. The producer of the Soul Wine in Cal' Haden has been discovered to be Christine, a lich. Her teacher: a Demon known only as The Sommelier. He was at the site, protecting a human wizard named Hugo. The Sommolier stated Hugo was "traversing the multiverse." No further information has been discovered of any of these people, other than the fact that Hugo has awoken...
It has also been discovered that The Inquisition of Callanhad is deeply entrenched in the production, distribution, and consumption of Soul Wine. There is currently an investigation led by Pendragon and James Du Bois to root this out.