A force known as Astral power permeates throughout the world, wielded by astral mages. Fearing its destructive power, the "Empire" persecutes those who show their abilities. The tormented mages then founded the Nebulis Sovereignty to flee from their oppressors. Since then, the two nations have been in bitter conflict, the war still going strong for more than a century. After committing the great crime of freeing an imprisoned witch, the talented knight Iska is sentenced to prison. A year later, the Empire leadership suddenly decides to set him free, with the condition that he hunts down a fearsome mage known as the "Ice Calamity Witch." Hoping to end the war, Iska agrees. Coincidentally, the Ice Calamity Witch herself, Aliceliese "Alice" Lou Nebulis XI, also wishes for peace and is willing to do everything she can to bring down the Empire. As Iska and Alice both yearn for a crusade that will turn the world into one without struggle, woe, or pain, the strings of fate tie them ever closer together, creating a bond that goes beyond something fabricated by mere coincidence. [Written by MAL Rewrite]

The final hour of the popular virtual reality game Yggdrasil has come. However, Momonga, a powerful wizard and master of the dark guild Ainz Ooal Gown, decides to spend his last few moments in the game as the servers begin to shut down. To his surprise, despite the clock having struck midnight, Momonga is still fully conscious as his character and, moreover, the non-player characters appear to have developed personalities of their own! Confronted with this abnormal situation, Momonga commands his loyal servants to help him investigate and take control of this new world, with the hopes of figuring out what has caused this development and if there may be others in the same predicament. [Written by MAL Rewrite]

Ainz Ooal Gown, the undead sorcerer formerly known as Momonga, has accepted his place in this new world. Though it bears similarities to his beloved virtual reality game Yggdrasil, it still holds many mysteries which he intends to uncover, by utilizing his power as ruler of the Great Tomb of Nazarick. However, ever since the disastrous brainwashing of one of his subordinates, Ainz has become wary of the impending dangers of the Slane Theocracy, as well as the possible existence of other former Yggdrasil players. Meanwhile, Albedo, Demiurge and the rest of Ainz's loyal guardians set out to prepare for the next step in their campaign: Nazarick's first war… Overlord II picks up immediately after its prequel, continuing the story of Ainz Ooal Gown, his eclectic army of human-hating guardians, and the many hapless humans affected by the Overlord's arrival. [Written by MAL Rewrite]

Following the horrific assault on the Re-Estize capital city, the Guardians of the Great Tomb of Nazarick return home to their master Ainz Ooal Gown. After months of laying the groundwork, they are finally ready to set their plans of world domination into action. As Ainz's war machine gathers strength, the rest of the world keeps moving. The remote Carne Village, which Ainz once saved from certain doom, continues to prosper despite the many threats on its doorstep. And in the northeastern Baharuth Empire, a certain Bloody Emperor sets his sights on the rising power of Nazarick. Blood is shed, heroes fall, and nations rise. Can anyone, or anything, challenge the supreme power of Ainz Ooal Gown? [Written by MAL Rewrite]