The Darkness is a corrupting substance, mostly manifesting as thick black goo. It can corrupt both the living and the dead.
The Darkness is a physical substance, as well as a concept. It can be seen as a thick, mucus-like oil, often moving under it's own power. It corrupts people, and slowly turns their nature towards it's own evil ends. These ends are those of chaos and destruction. No-one knows why, or from where it comes. Sometimes those infected with the darkness can plan for years, some others simply descend into animalistic frenzy. It is rumoured that some can withstand it's affects, but rumours such as these can kill.
The Darkness is so named both because of it's colour (a dark black), and because of it's aversion to fire. Light, in great intensity can have an affect. There is no known cure for those who have been corrupted by The Darkness.
Many assumed that Darkness was connected connected with the moon, but Tennebris strongly denies all associations with it. Despite this, and the general acceptance of the other Gods that it was nothing to do with Tennebris, the followers and priests of Tennebris have dwindled.
It was then not seen again until 1018, when it was encountered outside of a small town called Market.