By 
The Kugane Maruyama-authored light novel series Overlord will be getting a fourth season of its anime adaptation, as well as a feature film project [Thanks, ANN!]. The announcement was made during a marathon broadcast of the first three seasons on Japanese video site NicoNico Douga, and also spread via social media:
『オーバーロードⅣ』制作決定！
ティザービジュアルを公開しました。
スタッフキャストは引き続きのメンバーでお届けします。https://t.co/tWAiKFcvmx続報は後日お知らせします。#overlord_anime pic.twitter.com/gKWYrsCFvv
— オーバーロード／TVアニメ公式 (@over_lord_anime) May 8, 2021
Director Naoyuki Itou and writer Yukie Sugawara will return to head up the staff, as well as character designer Satoshi Tasaki. The announcement was accompanied by key art for the new anime season, officially titled Overlord IV. Artist so-bin, original character designer and illustrator for the novel series posted new art of protagonist Ainz and his companion Albedo commemorating the occasion.
４期！ pic.twitter.com/Lb22ltFMBL
— so-bin (@soubin) May 8, 2021
Overlord stars Satoru Suzuki, a player of the online RPG Yggdrassil who is the guild master of the high-level guild Ainz Ooal Gown. On the last day of Yggdrassil‘s service, Suzuki logs in, and finds out he has been incarnated into body of his game character, the undead sorcerer Momonga, and the NPCs populating his guild headquarters have been made real. However, the guild hall and he himself have been transported to an unfamiliar, magical place.
Over the course of the series, he adopts the name of his guild – Ainz Ooal Gown – for himself, and establishes a kingdom called “The Nation of Darkness.” The story also follows native inhabitants of the new world reacting to the sudden appearance of an overwhelmingly powerful and apparently monstrous faction.
The first three seasons of the Overlord anime adapted the first nine light novels (from Overlord Vol. 1: The Undead King to Vol. 9: The Caster of Destruction), and the fourth season will pick up at Vol. 10: The Ruler of Conspiracy. That volume begins after Ainz officially founds the Nation of Darkness by violently annexing territory from nearby countries, among other deeds. It seems safe to assume that the season may also dip into events from Overlord Vol. 11: The Dwarven Crafter, as well. That’s because a film project was also announced, which will adapt the “Sacred Kingdom” story arc from Overlord Vol. 12 and 13.
The Overlord light novels are available in physical and digital bookstores. The three available seasons of the anime (as well as two compilation films) are also on various streaming services, including Crunchyroll. Crunchyroll Games also published a localization of the mobile game Overlord: Mass for the Dead, but shut down service on March 31, 2021 (it continues in Japan).
