Causality (原因結果 Genin Kekka?) is the law of cause and effect in the world of Berserk. It is a force that influences a person's situation and even emotional states, which are tempered through years of careful, causal manipulation.
All of the world is bound in an endless chain of events, which lead to more causes and thus, more effects. This repeats in an endless cycle until the Idea of Evil fulfills its original intent. But nothing is written in stone as Guts, called the "Struggler" by the Skull Knight, defies his fate to die during the fifth Eclipse. Despite this, Guts' survival alongside Casca, made possible by the Skull Knight's intervention, only triggers unpredictable effects that barely affect the inevitability of the predestined timeline's general design.
While those like the Skull Knight use their experience of causality's flow to appropriately prepare for it, Void and the God Hand embrace the concept wholeheartedly and orchestrate situations to meet planned events. Such events involve the use of the Behelits, specifically the Crimson Behelit.
- The Idea of Evil is created, born from the collective subconsciousness of humanity when people seek answers for their existence. Acting on this collective need, the Idea crafts a method of delivering a savior for the world: manipulating bloodlines with Griffith as the eventual result. In time, subsequent members of the God Hand are recruited to prepare the events necessary for Griffith's rise and fall.
- The birth of Guts, a child saved from death by exposure to be raised by mercenaries and later struggle throughout his life before meeting Griffith, occurs.
- Griffith is born and grows up in the slums, gaining a desire for a kingdom of his own that is cemented with the Crimson Behelit he receives from an old fortune teller. Griffith later forms the Band of Hawk and recruits Casca.
- As Griffith rises to rank in the Midland court, Guts considers leaving the Hawks after overhearing his leader's ideals following the swordsman's assassination of Julius at his behest. Guts would later go through with it a month after the One Hundred Year War and covert removal of Griffith's opposition.
- Shocked by Guts' departure, Griffith suffers a lapse of judgement and has a one-night stand with princess Charlotte. This would lead to his arrest, the Band of the Hawk becoming wanted criminals, and their leader becoming maimed and crippled from a year of torture.
- Guts returns and saves Griffith alongside some of the Hawks. As he gradually learns the extent of the damage done to his body, Griffith has a vision of himself. As he follows it, he takes a cart to the location where the Eclipse is to occur. His followers reach him as he finds his activated Behelit, triggering the arrival of the Eclipse. There, reminded of the person he has always been while learning of the part he is to play in the Idea of Evil's grand design, Griffith sacrifices the Hawks to become reborn as Femto. Only Guts and Casca, violated by Griffith with her and Guts' unborn child being deformed into a fetus-like monstrosity as a result, escape death with help from the Skull Knight. But the deed is done and Griffith's rise to God Hand status marks the eventual beginning of the Age of Darkness.
- Fueled by his drive to kill Griffith, Guts trains himself to hunt for Apostles in hopes that one among them will lead him to the God Hand. Two years after Guts began his fruitless search, calamity and horrors befall Midland with a plague prompting people to take refuge in the city of St. Albion and the Kushan leader Ganishka sending his army to conquer Windham. A nameless Apostle, enraptured by his desire to bring about a new world, is part of the Incarnation Ceremony in St. Albion. The Apostle eventually swallows the fetal creature and sacrifices itself to to serve as Griffith's new body.
- Griffith's resurrection prompts the Age of Darkness, gathering Apostles to serve under him as his new Band of the Hawk while appearing as a savior to the Holy See and most of humanity. Ganishka, an Apostle who refused to follow Griffith, wages war against him, ending with his death and the invoking of the World Transformation. Griffith takes advantage of the global Interstice with his city Falconia protecting humanity from the various creatures of the Astral Plane that now inhabit the physical world, cementing his rule.