"Clash of the Berserkers"- Fate/Zero

The Holy Grail War is a ritualistic battle fought to determine who is worthy of commanding the Holy Grail: an omnipotent wish-granting device. The war is held between seven mages, each armed with their own familiar, an ancient heroic spirit of legend.

The Einzberns, a major contender in the grail war, have recruited the infamous mage killer Kiritsugu Emiya as their representative in the Fourth Holy Grail War. Though armed with his own arsenal, Kiritsugu is faced with six other mages vying to win. From bettering humanity to garnering respect, all opponents have their own reasons for seeking the Holy Grail.

But the grail war has been altered as a new servant is summoned by the Einzberns. A man garbed in black who wields a blade bigger than his own body. Who is he and how is he connected King Arthur? This servant who is also a berserker is an anomaly to the church itself and all of what is known of the grail. Kiritsugu Emiya will have the odds stacked against him in this Holy Grail War, but can his servant turn the tide?