Griffith, who is reborn as the demonic Femto during the Eclipse, is the central figure of the Golden Age Arc and the primary antagonist of the narrative. Initially introduced as the charismatic and brilliant leader of the Band of the Hawk mercenary group, Griffith is a figure of extraordinary ambition, beauty, and tactical genius. His driving motivation is a deeply held dream to obtain his own kingdom, a goal he has nurtured since childhood. To achieve this, he proves willing to employ any means necessary, including assassination, political manipulation, and even selling his own body, viewing the people who follow him primarily as tools to realize his ambition rather than as equals or friends.

Throughout the Golden Age, Griffith cultivates a relationship with the protagonist, Guts, that is both complex and possessive. After defeating Guts in a duel and forcing him to join the band, Griffith develops a particular attachment to him, treating him differently from any other subordinate and even risking his own life for his new recruit. This bond creates tension with Casca, Griffith's loyal lieutenant who resents the preferential treatment but harbors deep devotion to her leader. Griffith's world view is articulated in a conversation with Princess Charlotte, where he declares that only someone with their own dream can be his friend, a statement that inadvertently drives Guts to leave the Hawks in pursuit of his own path. Griffith experiences Guts's departure as a profound betrayal and a blow to his ego, leading him to make the reckless decision to seduce Princess Charlotte. This act of petty revenge and hubris results in his arrest and a year of brutal torture that leaves him physically shattered, mute, and crippled.

At his lowest point, after being rescued by his loyal soldiers, Griffith's weakened state and his inability to control those around him culminate in a final act of desperation. Upon witnessing a solar eclipse, his Crimson Behelit activates, summoning the God Hand, a group of demonic angels. Presented with the chance to be reborn as Femto, the fifth member of the God Hand, Griffith is told that the price is the sacrifice of the Band of the Hawk. In a moment of cold resolve, he chooses to abandon his humanity, declaring that he will not betray his dream. He willingly sacrifices his entire mercenary band, who are then brutally slaughtered by demonic Apostles.

As Femto, Griffith's appearance transforms into that of a dark, winged entity with clawed hands and feet, resembling a sinister hawk. In this form, he demonstrates newly acquired divine abilities, including telekinesis, the power to manipulate gravity and space, and a charisma so immense it inspires worship rather than mere loyalty. His personality crystallizes; he becomes utterly unburdened by morality, empathy, or human connection, focusing solely on his sovereign dream. In the most horrific act of the Eclipse, he uses his power to rape Casca in front of a horrified Guts, an act motivated by spite, a desire to reassert his broken dominance, and to inflict the deepest possible wound on the man who he felt abandoned him. This event forever brands Guts and Casca, cursing them to be hunted by evil spirits and setting Guts on his path of vengeful pursuit. The development from the untouchable, angelic leader of men to the demonic and utterly inhuman Femto represents the complete subordination of all human bonds and morals to a singular, all-consuming ambition.