Last Guardian Of Nazarick
When The Great Tomb of Nazarick was first captured there were 6 floors originally with its own NPC defending each floor or people would call them - Floor Boss. It was very difficulty for many Yggdrasil players to conquer the dungeon because of the presented challenges in the tomb
However the Guild named as Ainz Ooal Gown which despite their first attempt successfully conquered said dungeon, and they have furthered the development and difficulty of the dungeon and have stretched the floors up to 10 and at the same time creating their own respective NPCs or what they call as Floor guardians
But unknowns to the Guild members there was 1 floor that they have not raided yet- The underworld.
it was true that the first 10 floors are no doubt like an underworld and possess many challenges that some may mistakenly it for a hell.
But this 'underworld' is nothing like what they've seen before-
- No history