Alum Sharr

Alum Sharr, formerly known as Avanchnzel, was a former city of the ancient Dwemer that was repurposed in the Fourth Era to serve as a stronghold. It had been rebuilt and subsequently occupied by the Autumnshade Coven. The entrance to this vast underground structure could be found at a high altitude in the southern region of the Rift, and it's interior stretched far into the Velothi mountain range.

Being the only stronghold of it's kind until 4E 183, Alum Sharr remained as the capital of the Coven's sphere of influence throughout its existence. It hosted the Chief Battlemage's court, the chambers of the Council of the Stainless Onyx, the Autumnshade Lexicon and portal to Styx Xasum.

Avanchnzel
Avanchnzel had been one of many dwarven cities that could be found in Skyrim, all of which had been abandoned when the Dwemer dissapeared. Based on the presence of a large, automated Animonculory, the city's export may well have been Animaculi. Within the cities population existed a doomsday cult known as the Szavith Mhulen, who built the portal to Styx Xasum in the early Second Era.

In the early Third Era, a group of explorers entered the ruins of the city, hoping to uncover ancient knowledge by harnessing a Lexicon they had previously discovered. All but one of the adventurers were killed under mysterious circumstances; and their death was attributed to the rogue Animaculi the Animonculory had been automatically producing for centuries. The single survivor managed to escape with the Lexicon however, having also shut down the Animonculory.

A few months after the Red Mountain eruption of 4E 5, tremors rolling across the continent dislodged a large sheets of rock in the Velothi Mountains. The resulting rockfall blocked off the entrance to Avanchnzel. Remaining spider Animaculi sent out a distress signal to the other lifeless cities, and set about clearing a small cave system leading to the surface.

First and Second Battles of Avanchnzel
In 4E 181, a group of vampires from the Phantomsnare Coven entered Avanchnzel, hoping to unlock a Lexicon that had been recovered from the Imperium Vaults. They faced vast numbers of Animaculi as they progressed into the ruins, but overcame the mechanical entities with only moderate casualties. This was shortly followed by the Second Battle of Avanchnzel, in which the ruins were captured by the Pale Orc's of Largashbur after a three-day siege spanning the city's depths.

Alum Sharr
The re-construction of Avanchnzel had began once the Pale Orc's had settled into their new lifestyles. It was completed on the 25th of Morning Star in 4E 182, and the Battlemage officially changed the stronghold's name to Alum Sharr; the Orcish translation of 'Broken Keep'.

After this additional work on the stronghold began to decline, as efforts instead went into building the puppet-town of Nasphödol to the north. The Boiler Room where the Lexicon was kept became a chamber dedicated to the Coven's valuable artifacts during this time. A hazardous gas leak following the Boiler's decommisioning resulted in the stronghold's thrall population being forced to move to Nasphödol, where they were needed to produce food for themselves and trade for the Coven.

Although scouted by enemy forces, neither the Silver Hand or Midnight Pantheon ever attacked the Broken Keep, instead attacking the more vulnerable Nasphödol, where the Coven had been forced to store their thrall population. The stronghold's trebuchet did serve as ranged artillery during the battle, and although enemy camps were out of range it's projectiles accounted for the deaths of many enemies on the battlefield.

*End of currently established canon*

Interior
Once established in Avanchnzel the newly-formed Autumnshade Coven began to quickly industrialize, converting many area's of the ruins into massive furnace chambers. Many new rooms were carved out from the rock, their designs being a hybrid of Dwarven and Orcish masonry. Once built the non-militant vampires took up residence in homes carved into the walls of the circular main chasm. Empty halls gradually became marketplaces where blood, thralls and other resources were sold. The Animonculory remained largely untouched, although the control room responsible for its automatic functioning was removed. Corridors past this were restricted for most stronghold-dwellers, and after the Activation dwemer mechanism traps were active in the lower halls. Avanchnzel's former Boiler Room could be found in the deepest chamber, which had been converted into the Coven's artifact chamber and the Battlemage's study room after the Boiler had been shut down.

Exterior
On the ground outside the gateway stables could be found that catered to horses and Grouwud. Wisp flame torches rested around the stone plateau at the entrance. This was preceded by a small stone staircase that ends long before the terrain evens out. An artificial tunnel boring into the mountain that is connected to the plateau marked the beginning of the Yuhan Pass.

Above the main gateway stood several rows of balconies, each sporting weapon emplacments facing towards the ground below. A rotation of Gurak-Orsim and thralls were stationed on these balconies throughout the day and night respectively to man the emplacments. Barracks were built into the rock above these levels. High above conventionally accessible levels trebuchets could be found on a sturdy platform; these were only accessible via an elevator connected to the stronghold's interior.