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GA.png Non-Canon: REMINDER! This page is considered as among one of the many pure game contents found exclusive in Mass for the Dead only. It includes the new standalone characters that had a first-time appearance in the game. Meanwhile, the old characters had a different role and fate than from the main storyline in the official books. For that reason, it has no connections to the canon story materials of Overlord Light Novel series. The content that you had read here are based on the Overlord mobile game.

Sewage Treatment Plant (汚水処理場です) is a facility located within the city of E-Rantel in Mass for the Dead.


The Sewage Treatment Plant serves as the main entrance to E-Rantel's underground sewer network.


Mass for the Dead Arc[]

Main article: Mass for the Dead Arc

After the protagonist of the game applied as an adventurer with the help of Saint Clementine, the latter asked him and his friends to take one of the jobs posted on the bulletin: "Underground Sewer Research Mission." It was a job that was deemed to be fairly easy as it was just to confirm the state of the local Sanitary Slimes in the sewers. Due to the large number of refugees coming to E-Rantel, the saint expressed her concerns that the increased waste would cause the slime population to explode. However, strangely the manager at the plant reported that the monsters' population didn't show any signs of proliferation. In fact, the sewers are being purified to a degree unforeseen before. When the protagonist, Slimeko, and Soi investigated they found that instead of the slimes undergoing mitosis like they normally do when well feel, they had grown into bigger forms and acquired a voracious appetites. After cleaning the sewers of the slimes, their team discovered a hidden room but could not determine its purpose as it had been abandoned. Later on, slime samples were brought back to their employer, Sophie Noia, who was eager to study why the slimes had underwent a rapid mutation.[1]

After Sophie Noia finished her assessment, it was determined that the slimes had mutated because they were exposed to alchemical solutions. It was believed that the substance was fed to the slimes intentionally, but later was proven to be an accident as residue from the nearby herb cultivation had gotten in the water via runoff and into the sewers. Now facing a serious problem of a slime infestation days away from the Tripartite Alliance summit, the protagonist and his team volunteered to go into the sewers to exterminate the slimes. The adventurer trio along with their comrade Sebas Tian entered and after killing all the giant slimes came across a Super Giant Sanitary Slime that had been overfed from the alchemical solutions from the water tank. They successfully kill it and brought back its core as proof to the city officials.[2]

Layout & Features[]

The treatment plant is located downstream within the city and composed of high walls in order to prevent slimes from spilling out into the city. The gates to the plant has a drop lattice that can be only opened by a single key.

  • Underground Sewers: The plant connects to the sewage system of the city.
  • Water Tank: A place where sewage collects and stores water.
  • Hidden Room: A secret chamber located within the Water Tank area, that can only be accessed through a panel in the wall.
  • Hidden Dungeon: A second secret chamber located in the sewers used by the demon Isabella as her personal area to feed and torture her victims.[3]


  • Originally, the hideout within the hidden room belonged to a shady organization. However, it was later abandoned after the formation of the Alliance as the Re-Estize Kingdom's nobles pulled all funding from their illegal deals to handle the Chaos Beast crisis.



Click on the images to enlargen them.


Re-Estize Kingdom
Re-Estize Ro-Lente Castle Magician's Guild Re-Blumrushur Re-Robel E-Naüru Re-Uroval E-Pespel
Baharuth Empire
Arwintar Grand Arena Imperial Castrum Ministry of Magic
Roble Holy Kingdom
Hoburns Kalinsha Loyts Prart Rimun Debone Great Wall Holy Kingdom Liberation Army Base
Sorcerer Kingdom
Great Tomb of Nazarick Log Cabin E-Rantel Katze Plains Carne Village Monument of Ruin Great Forest of Tob Abelion Hills Great Lake Underground Tomb
Elf Country
Crescent Lake Great Forest of Evasha
Dwarf Kingdom
Feo Jera Feo Berkana Feo Teiwaz Maze of Death Great Rift Feo Jera's Garrison
Other Locations
Eryuentiu Azerlisia Mountains Sea City Sasasharu Ruins Silent City Bown Swamp Rhynd Sea Sewage Treatment Plant Vadis Free City Quarry Tide Pool