This is Yûlash, it used to be a fort town near the border of two warring nations. In a desperate attempt to prevent an invasion, a commander gave green light to a wizard to open a portal to the abyss to unleash demons on their enemies. Needless to say, that did not work and both armies were decimated by the demons. The place is now mostly abandoned and groups of soldiers patrol the nearby areas to make sure the demons stay inside rather than outside.
The attached PDF includes background info, the map key and some adventure ideas. The maps included in the Patreon-only release come in different variations, notice that some of them do not include the town name in case you want to name it differently.