Berserker is a Berserker-class Servant able to be summoned by the Protagonist in the Grand Orders of Fate/Grand Order.
IdentityBerserker's True Name is Ibaraki-douji.
During the Heian period, one of the Oni that appeared on the imperial capital and exhaustively carried out atrocities. Regarded as a subordinate of the Shuten-douji that lived in Mt. Ooe, it has been said that - during the "oni extermination of Mt. Ooe" by Minamoto no Raikou and her Four Heavenly King - she crossed sword with Watanabe no Tsuna of the Four Heavenly King.
The sole survivor of Mt. Ooe's oni, she attacked Watanabe Tsuna on the Rashoumon (or the Ichijou-modoribashi) at the imperial capital and ended up having her arm cut off. While said arm was temporarily snatched away as a spoil of war, Ibaraki would later retrieve it and disappear to somewhere.
In actual fact, she is not Shuten Douji's subordinate, but it is rather believed that Ibaraki Douji existed as "the ringleader of Mt. Ooe's oni". (Despite being a mighty existence, the extremely pleasure-seeking Shuten had no intentions of commanding the swarm of oni herself)
The one who erected a solemn palace at Mt. Ooe, cherished Shuten Douji as a sworn brother, commanded a group of oni that were each a match for a thousand warriors and exerted tyranny on ancient Kyoto was Ibaraki Douji herself; a "raging oni" that made people fall into the depths of terror.
Due her anecdotes and vestiges, she is classified as a "anti-hero"
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