Mine Dungeon

Mine Dungeon (鉱山ダンジョン) is the tentative name for a mine under the rule of the Great Tomb of Nazarick in Mass for the Dead. To prevent incursion by humans it was temporarily converted into a Dungeon by Demiurge.

Background
Originally a mine belonging to the Re-Estize Kingdom but was abandoned and later became inhabited by various monsters. After the Catastrophe, the mine was found by Demiurge, who under the orders of Momonga began extracting the ores within. The ores were planned to be sold into the New World, as the human nations were now in a perpetual state of war with the appearance of the Chaos Beasts. The ores being converted as a source of income would then be used to fund the repairs for the damages the Great Tomb of Nazarick suffered during the Catastrophe.

Mass for the Dead Arc
The protagonist and Slimeko working as adventurers in E-Rantel attended a meeting of other high-ranked adventurers called by the guildmaster. At the meeting the two see Blue Roses present forewarning something serious is about to occur. Pluton Ainzach arrives to call the meeting into order to discuss the state of the world and the rising prices of ores for weaponry and armors. Under a royal edict the King requested the aid of the Adventurer's Guild to reclaim a mine north of E-Rantel to gain a new source of metals. Though the guild was supposed to maintain neutrality in national affairs, the guildmaster deemed the state of affairs in the world to be an exception and the necessity to acquire new resources imperative. The protagonist and Slimeko realizing that the mine the adventurers would be sent to reclaim was the one Demiurge was stationed at, reported to Momonga of the developments. Momonga having been delivered the news called a meeting of the Floor Guardians to address this issue. The group did not wish to relinquish control of the mine, nor did they wish to attract unneeded attention to themselves. Demiurge had predicted a scenario like this and proposed a plan. Calling it his “Mine Dungeon Project”, the demon proposed to turn the mine into a “dungeon of death” in order to not only wipe out the adventurers but also dissuade any future investigations once word of the deadly hazards of the mine would spread to the human nations. As the adventurers would require time to prepare to reach the mine, Momonga approved the idea and gave Demiurge a troop of skeletons for his use and ordered him to proceed.

At the mine Demiurge planned to minimize the resources Nazarick needed to convert the mine into a dungeon. To do so he enlisted the aid of Entoma Vasilissa Zeta, who used her abilities to subjugate the insect monsters present in the mine as their minions. Mare was contracted to assist in altering the internal structure of the mine to Demiurge’s specification. Abyss Demon provided his aid by creating the perfect cover story for the mine, as the den of a demon and provided the necessary props to making it look convincing. He was also installed as the nominal boss of the dungeon and waited alongside his master for the adventurers to arrive.

When the initial adventurers came to the mine, they were the first to be claimed by the mine. Blue Roses leading the next batch of adventurers came to find their corpses crucified at the mouth of the entrance. The group was horrified by the display, but those in Blue Roses noticed that this work was not done by mere monsters and hinted some sort of intelligence. They enter, press forward slaying skeletons and hanging spiders in their path. Lakyus though notices that the color of the walls were different between the parts that have passed the age and those that do not. It indicated that the mine was altered in some way. Evileye suggested that earth type monsters could be responsible though Gagaran doubted that even they could pull something off in such a short time. Gagaran abruptly hits a wall revealing a Hanging Spider and kills it. The discovery causes them concern as insects do not normally follow undead.

Coming to a fork in the tunnel which is not on the map. Certain that some intelligence had taken over the mines, Blue Roses takes the old tunnel, believing it to lead deeper into mines while the other adventurers take the newer route which they believe to be safer. Traveling through the tunnel, Gagaran becomes uneasy and Evileye discovered the scent of blood. A blood character is found written on a wall. Deeming it to be no trap the group investigate it to be part of some ritual. An imp suddenly attacks them and the party quickly kills them. The appearance of the demon causes Blue Roses to be concern as its appearance in a mine should not be. Finding a drawing in blood on the ground with an animal sacrifice, they are attacked by another imp. After dispatching the creature they turn back to their findings an determine that the geometric shape of the symbol to be part of a demonic summoning ritual. Additionally they discover bodies with their internal organs removed and a book with foreign words, the same as the one on the walls and floor. It is believed to be a magic book specializing in summoning demons.

Layout and Features
The mine was radically altered by Nazarick and converted into a dungeon. Mare transformed the tunnel into an intricate shape to lower its visibility to force more adventurers to more spend energy on detection. A forked tunnel was also included with the intent to separate the adventurers to commit them to longer searches to eventually exhaust their stamina. Mare used his power to superficially make it appear that the tunnels went in all directions. Along the tunnels there were places that allowed monsters to hide away in order to ambush them in a trap. Additionally traces were intentionally left behind by Demiurge to show that the mine was a site of demonic summonings, using foreign characters traced in blood and corpses of would-be summoners and tomes detailing in demons.

Trivia

 * Demiurge while creating the dungeon in the mine, had intended to create it as a site which would impact a worldview on the New World, so much it would inspire fear and terror to prevent further attempts at exploration.