When you’re playing a dying VR game, and you fail to log out when its servers all go offline….
While the game was still active, Momonga and his guild comprised the highest-level, most skilled players the game ever had. The mansion their guild inhabited was set up as a dungeon to end all dungeons in the game, with NPC’s (the “Pleiades”) patrolling each level that were usually more powerful than most every other player in existence.
Then came the day the VR-supported MMO game was to close its servers for good. After fiddling with Albedo’s programming, Momonga decided to sit about to wait out the shutdown just to see what would happen.
Unexpectedly, he became the Overlord of a whole new world within which his mansion was plopped into. NPC’s now had their own will and character, and now Momonga had an Albedo who will forever be madly in love with him (and no way for him to undo it).
As the only remaining guild member, Momonga changes his name to “Ains Ooal Gown” — the original name of the staff that embodies his guild.
The remainder of Overlord is his adventures in this new world….