Spoiler Alert: WARNING! This page happens to contain a lot of heavy spoilers that are all originated from the Overlord author, Kugane Maruyama and his collection of written works. Anime-only watchers and Manga-only readers, please take some time off to reflect it over for a bit before choosing to expose yourself on reading the information below recklessly.
Round Table Room is described to be a gigantic table carved of gleaming black stone sat in the center of the room. The guild's insignia is embedded within the middle of the table. It is surrounded by forty-one luxurious chairs where each one was positioned around in a circular pattern.
The room is most likely a reference to the Arthurian Lore of the Knights of the Round Table.