|Beast of Darkness|
Personification of Guts' Desire for Vengeance
The Beast of Darkness is the manifestation of the darkness within Guts' soul.
Assuming a wolf-like form, the Beast of Darkness is inky black with demonic, red, lightning-like eyes. After it is "tamed" by Schierke, several chains are shown tied around its body. However, the beast is shown to be able to break them by using its mouth that is full of sharp teeth, as its power and size grow with time and with every repeated use of the Berserker Armor.
The Beast of Darkness has been mainly shown with its demonic left eye, corresponding to the damage that Guts had sustained to his right eye.
The Beast of Darkness is a personification of Guts' wrath and bloodlust, born from the trauma of what he's experienced in the Eclipse, the stress of losing his allies and Griffith's betrayal driving him to homicidal rage. Like Guts, the Beast hates Griffith and refers to him as a light that burns. As some restless spirits explained, the beast becomes stronger each time Guts takes a life and thus subconsciously encouraged the swordsman to commit mass slaughter for two years. It is only when Guts starts to regain bits of his humanity that the beast refuses to allow this and makes numerous attempts to force Guts to resume their carnage. It sees Casca and Guts' new allies as frail enablers of its host's morality, and believes said morality can be eliminated by killing them all. Yet it also encourages Guts to cherish them, as their deaths would drive the swordsman into a deep enough despair that the beast would swallow him whole and resume the hunt of Griffith unopposed. Whenever Guts uses the Berserker Armor, especially during the night of a full moon when its influence is strongest, the beast tries to take control and increases in size every time it is called.
The beast also represents Guts' lust, as it showed a strong attraction to Casca and forced Guts to hold her down and kiss her. It also showed Guts visions of itself ravaging Casca before biting her head off, as an attempt to sever Guts' humanity. However, it only manged to make Casca scared and distrustful of Guts. It strongly desired for Guts to "rip her up like Griffith did" .
The only things that can stop the Beast are Schierke's magic (though the Beast can sometimes resist it), Guts' own willpower (though he can no longer stop himself when encased in the Berserker Armor) and, most notably, the Moonlight Boy, who can effectively stop the Beast from attacking and show Guts the light, guiding him back to self-control (using his love for Casca). Guts seems to remember the boy's light clearly despite usually blacking out when under the Beast's influence.
As Guts took a path of revenge of blood and carnage after being rescued by the Skull Knight, the beast grew stronger with each kill Guts made for two years. It was only when Guts became conflicted after being forced by Jill to spare a dying Rosine that the beast finally made itself known to Guts by using a group of restless spirits taunting the swordsman over his recent actions as a temporary vessel to manifest through. The beast explains its origins to Guts, showing no remorse over its host being forced to kill children that Rosine made into her familiars, and tells him that they will become a monster like Griffith someday. In a fit of rage when the beast assumed Griffith's likeness, Guts drives the apparition back into his mind. When Guts received a vision about Casca being burned, the beast manifests again within Godo's mine to mock Guts before vanishing.
Millennium Falcon Arc
While Guts desired a life of peace with Casca, the beast refused to allow that to occur and takes advantage of the endless hordes of spirits to mock Guts while convincing him to give in to his darkest desires. This ultimately causes Guts to lose himself with the beast taking control and attempting to have its host ravage Casca before murdering her. Though Guts stops himself in time, the beast succeeds in having its host lose Casca's trust in him with Guts being forced to align himself with Farnese de Vandimion, Serpico, and Isidro to protect Casca in case he loses control again.
The beast later makes its presence known to Guts' newly formed group when he dons the Berserker Armor. As the armor intensifies violent emotions as a form of pain killer, Guts suffering an ethereal wound from fighting Slan prior, the beast used it to completely possess Guts while altering the armor in its image. However, usually through Schierke's astral projecting herself onto him, Guts can regain control and was able chain his inner beast once again. The beast continually urges Guts to give in to his dark desires of killing Casca and his new allies so they can resume his hunt for vengeance without concern for the lives of others.
- Similar to the Idea of Evil, which was born from the collective subconscious of humanity, the beast is more like a personal construct of Guts' subconscious.
- While not seen in the earlier story arcs, his presence is felt whenever Guts fights an apostle and goes berserk.
- The Beast of Darkness is referenced in the video game Bloodborne, via a boss called The Watchdog of the Old Lords, and also appears as a mini-boss in Dark Souls 3. It most resembles The Beast of Darkness when it was consumed in flames within Guts' mind.
- It is commonly nicknamed "The hellhound" by fans, due to it's appearance.