Overlord Web Novel

This is the original version of the Overlord series written by Maruyama Kugane (丸山くがね) under the same name. It is divided into two parts and is still being updated periodically.

The former part can be found here, and the latter part here.

Plot
The story begins with YGGDRASIL, a popular online game which is quietly shutting down on its last day. Our protagonist Momonga decided to stay until the last moment in his beloved game and wait for the force log out. Unexpectedly, the server did not shut down and Momonga is stuck in his skeleton body and transferred to an unknown world. "The Powerful Overlord" now needs to face the New World and continuous challenges.

List of Characters that do not exist in the Web Novel

 * Albedo
 * Mare Bello Fiore
 * Nigredo
 * Rubedo
 * Victim
 * Hamsuke
 * Nfirea Bareare
 * Pulcinella
 * Six Arms: Zero and Succulent exists, yet they are just members of the Eight Fingers.

Characters that only exist in the Web Novel

 * Fay Bareare: Granddaughter of Lizzie Bareare.
 * Gignal Elshy:Hight Priest of Earth in E-Rantel.
 * Ishpen Ronble: Adventurer's guild receptionist.
 * Jet Testania: A student at the Magic Academy in the Baharuth Empire.
 * Leberina: 3rd of the Six Arms. Hybrid class of Duelist and Magic Caster.
 * Unnamed Floor Guardian of the 8th Floor: The strongest NPC character of Nazarick.
 * Wina Harshia: Adventurer's guild receptionist.

Other differences of Characters

 * Ainz Ooal Gown: Racial level is different (Skeleton Mage (15) / Lich (10) / Overlord (10) / Demi Lich (5)). Ainz's World Item is "Avarice and Generosity".
 * Aura Bella Fiora: Her name is Aura Debay Fiora.
 * Clementine: She is not related with the Cemetery Incident. She was introduced in the second part of the Web Novel.
 * Cocytus commands his own troop of beetle warriors and is the head of security for Floors 9 and 10. He was created by Blue Planet.
 * Demiurge: As Albedo doesn't exist, Demiurge is the overseer of the Floor Guardians. Also, his appearance is much more like normal devil's - He is 2m tall, has red skin, black wings and horns.
 * Lupusregina Beta: She is not a sadist, just a cheerful character who loves to eat.
 * Narberal Gamma: Her level is 57.
 * Shalltear Bloodfallen: She is not the strongest Floor Guardian. Also, she does not have Valkyrie/Lancer class. Instead, her cursed knight class level is 10.
 * CZ2128 Delta: Created by Tabula Smaragdina.
 * Swords of Darkness: The name of the team is "Axe of Cyclone".

Overlord Volume 1

 * Attack on Carne Village is not related with the Sunlight Scripture.
 * Gazef spars with a Death Knight by Ainz's request. As Death Knights are specialized in defense and not good at attack, the fight ends in a draw. (Ainz withdraws the Death Knight and tells Gazef that he's the winner)
 * As a result, Ainz does not have a chance to confirm the world's power balance, and the Slane Theocracy does not notice the existence of Nazarick for now.

Overlord Volume 2

 * Instead of Ainz, Narberal Gamma becomes the Adventurer "Momon" alone, using illusion magic.
 * Brita, whose name is Baniara in the Web Novel, uses the same room with Momon. Since she does not like the smell from the herbs used to cure wounds, she gives a Minor Healing Potion to her.
 * While the Swords of Darkness did not exist in the Web Novel, Momon confronts the Axe of Cyclone instead.
 * "Momon" first works as a porter of the Axe of Cyclone. So they didn't die and go their separate ways without an incident.
 * Lizzie Bareare tries to learn how to make red potion from Momon directly, but is refused.
 * Momon defeats Khajiit Dale Badantel by chance during his promotion test.
 * Momon introduces himself as an apprentice of Ainz Ooal Gown.

Overlord Volume 3

 * Shalltear succeeds in catching Brain Unglaus, making him one of her servant vampires.
 * Thus, Shalltear does not encounter the Black Scripture and become mind-controlled.
 * This makes the whole story in Volume 3 quite short. The chapter "True Vampire", which is the base story of volume 3, is contained between Momon's first request with the Axe of Cyclone and defeating Khajiit Dale Badantel.
 * Momon introduces Shalltear as 'Camila', one of the three apprentice of Evileye.
 * Treasury was described in a side story.

Overlord Volume 4

 * Main story remains quite the same. Just some 'daily life' parts of Nazarick are added in the Light Novel version.

Overlord Volume 5

 * Main story remains quite the same. Blue Roses is described with more details in the Light Novel version, related with Momon.
 * Sebas Tian and Climb part ways after training. Climb returns earlier, he tells Renner and Lakyus about Sebas and the brothel. He was sent to rescue slaves.

Overlord Volume 6

 * Only Demiurge comes to the capital, having a short battle with Blue Roses before returning.
 * Demon invasion does not occur. Sebas Tian destroys the Eight Fingers on his own.
 * Sebas saves not only Tuare, but also other women captured by the Eight Fingers.
 * Renner assumes Sebas and Demiurge are connected with someone, possibly their master.

Overlord Volume 7

 * Events take place before the Men in the Kingdom's arc.
 * Ainz decided to become a legendary figure in the Baharuth Empire.
 * Since Hamsuke doesn't exist, Erya Uzruth was killed by the Vampiric Brain Unglaus.
 * Arche Eeb Rile Furt becomes Shalltear's sex toy and she also teaches Ainz how to dance.
 * Arche's twin sisters lived with their older sister in Nazarick after Ainz save them from slavery.

Overlord Volume 8

 * Enri's story is shorter due to the lack of Bareares.
 * Three Monsters don't exist. Enri goes to E-Rantel to sell herbs, where she meets Fay Bareare.
 * Lupusregina Beta's behavior is modest. She brings smiths, weapons and armor for goblins and ogres.
 * Axe of Cyclone visits Carne Village, they encountered and surrendered to Enri's goblins. Enri apologizes for the inconvenience. The rumors about unusual village start spreading among the city's guards.
 * Nazarick's side story was written only for the Light Novel.

Overlord Volume 9

 * The Emissary of the Kingdom visited Nazarick and was killed by Ainz after he insulted his Guild.
 * Emperor Jircniv sent an elite scouting team to observe Nazarick, but they were captured by Aura.
 * Fluder Paradyne quits his position immediately after encountering Ainz to become his disciple.
 * The Re-Estize Kingdom sends 1,000 men to capture Enri, and they end up being killed by 30 Redcap Goblins.
 * Since Mare doesn't exist, Fluder Paradyne is with Ainz during the massacre at the Katze Plains.
 * Gazef Stronoff survived the massacre while Marquis Raeven was trampled by the Dark Young.
 * Since Ainz doesn't establish a nation, E-Rantel became part of the Baharuth Empire.
 * Ainz becomes the most powerful noble in the Baharuth Empire, whose authority rivals that of the emperor.
 * The Second part of the Web Novel deviates completely from the Light Novel.

Trivia

 * It began serialization online in 2010, before being acquired by Enterbrain.