The City of Kalaetha: some background

Kalaetha (kuh-lay-thuh) is a city beneath the Quarinth (kwar-inth) Mountain. It is not incredibly noticeable from afar for this reason. You might come within several hundred feet of one side of the mountain and not know that within is a very large, densely populated, and bustling city. The cavern in which the city is located is incredibly large spanning many miles across and the excavated ceiling of which is more than 150 feet tall toward the center. The layout of the city is memorable as well. The buildings in Kalaetha are all laid out in concentric circles getting larger and larger as you get farther from the center of the city. The walls of the buildings are more and more concave the farther into the center of the city you go.

 A very notable landmark in Kalaetha is the enormous octahedron that is suspended in the very center of the city. It hangs from four giant chains that are connected to the corners of the octahedron. The purpose of the enormous hanging object is clear when you look at it. Kalaetha being an under mountain city has no natural light. The Sunstone, as it is called by the locals, provides an easily manipulated amount of light to the entirety of Kalaetha by the Mages who preside over it. 

Kalaetha is famously the site of a mine for the stone of the same name as the mountain under which it resides, Quarinth stone. This stone is widely sought after because of its innate ability to hold lesser magical properties far easier than other materials, which makes it an excellent choice to set in rings and amulets for enchanting purposes. Kalaetha has always been a center of trade and practice of magic because of the natural want to work with the quarinth and its value to those in other parts of the land. 

The Sunstone in the center of Kalaetha is actually made up of many smaller Quarinth stones that are imbued with a light spell. The lighted stones are covered and uncovered at set times to produce a day and night effect in the city. It is very crude compared to the slow transitions of the real solar and lunar cycles.  

 Kalaetha is a newer city. Which is unremarkable because one of the only reasons that it exists is for the market of quarinth stone. The Mountain that the mine and city are under is well out of the way and is no place for starting a civilized city without already having some ability to get resources from trade somewhere else. There is very little inside of the Quarinth Mountain that doesn't come from trade with other cities. 

Two weeks prior to the summoning of adventurers from realms beyond by the halfling Elanveril.
It rained for the first time in Kalaetha, ever. It was black rain. The rain began pooling and coming together and becoming viscous. The viscous black rain began to move on its own. Someone was engulfed in a public area by one of the black, purplish oozes. Many people couldn't escape. The oozes actually move quite fast. The oozes start devouring everything organic in the streets. the oozes continue to patrol to this day.

The Guard of the city try to fight back but are ill-equipped to deal with the oozes. Whenever they strike the oozes just split into smaller versions of themselves and recombine at their earliest convenience. The guard slowly becomes more and more fractured as it is hard to travel the streets. they hole up wherever they can.

To make matters far worse, the doors of Kalaetha start leading to otherworldly places. They do not lead into the places that they seem on the outside. Leaving a building is not as difficult but it still is not where you thought you would end up. That is, all of the doors in Kalaetha never lead directly to where they open to. If you are trying to enter a building it takes you to a pocket dimension dungeon. Once any part of you enters it cannot be taken back out. There is always a way out through the dungeon. The way out of the pocket dimension does always lead to the building you were trying to enter.
If you are trying to leave a building in Kalaetha it will randomly lead to another section of Kalaetha. (I determined this by Hex-Grid) all the doors of that building always leads to the same place after determining the first time where it leads.

Dudegrin Stormguard is the captain of the guard in the North Barracks of Kalaetha. A while back he and is friend who runs the Comely Crock, an inn residing in Kalaetha, came up with a plan to build a tunnel between the barracks and the inn. They succeeded and it saved Dudegrin life. The doors to the barracks were open and the oozes came rushing in. Dudegrin was the only one there at the time all the guards being on duty elsewhere. Dudegrin himself was just coming back for a potion he had stored so he could return to help the people. Alas, he had to escape through to the Comely Crock and seal off the tunnel for fear of being followed. It was there that he and his friends Elanveril and Gwenlynor the Innkeepers summoned the heroes in about a weeks time.