Considered by many as the pure personification of strength and will, Guts is a byronic hero who is born as one who may be able to struggle against causality but who is unable to maintain it indefinitely. The second story arc of the series revolves around his childhood and adolescence in a mercenary band after being adopted by the band's leader Gambino, and his later joining of, and departure from, the Band of the Hawk.
The dynamic and turbulent relationship between Guts and Griffith, the leader of the Band of the Hawk, forms the primary focus of the manga for the first thirteen volumes. After the events of the Eclipse, during which he loses his left forearm and right eye, Guts seeks revenge on Griffith, who is now Femto. In the process, he is reunited with Casca after a separation of two years.
Following the Incarnation Ceremony at Albion, Guts travels with a new group of companions.
Guts can be seen as the exact opposite of Griffith in just about every way. Guts is a tall, muscular warrior with short black hair, a body full of scars and wields a monstrous weapon. Griffith is of average height, thin, has long white hair, no scars and wields an elegant rapier. Guts wears tattered black clothing and, though incredibly skilled, fights like a barbarian; winning by any means necessary. Griffith wears white armor and has a much more refined style resembling fencing. In addition they usually have the exact opposite effect on everyone they meet. Most people are naturally drawn to Griffith upon first meeting him and would die for him without hesitation. Guts however is usually feared and detested by just about everyone he comes across. This extends to their morals and intentions as well. Guts usually refrains from involving others in his plights whereas Griffith rarely dirties his own hands. Griffith freely manipulates others caring only for his ultimate goal, while Guts (though he would never admit it) values the lives of others and strives to protect them.
Guts is depicted as a tall, muscular man, standing from 6'4 or even taller with short, spiked, black hair in a crew cut. He is missing his left forearm and right eye due to an encounter with the Godhand and is covered head-to-toe in scars, with the most notable being a lacerated scar on his nose. After receiving the Berserker Armor, Guts receives a small fringe of white on his hair, presumably due to the stress brought on from wielding the armor. Guts' tendency to wear black clothing while hunting the Apostles gained him the nickname 'The Black Swordsman.' Aside of all this, Guts has a brand on the back right side of his neck that attracts demons and evil spirits to him at night, as a result of the Eclipse.
Guts' original design, featured in the Berserk Prototype, had him wearing an eye patch.
Considering the fact that he is just a normal human, Guts is considered a grandmaster swordsman of no ordinary level and skill which shows up in every battle or duels that he partakes, specially when he is engaged with demonic beings. He is also skilled at using many bladed weapons, has knowledge on how the mechanism of complicated firearms work and is also a good horse rider. Despite his large frame he is very fast, dexterous and agile for a human of his size and stature which can be seen when he is engaged in combat with multiple enemies.
Guts' ferocity, fury, aggressiveness, and strength do much to conceal the cunning person within him. He is very perceptive, quick witted, clever, and a skilled strategist, which goes hand in hand with his strength. These are major reasons of why he had survived the countless encounters that he so far had faced. A good example of his tactical prowess is his fight with the apostle Rosine. During the fight Guts was severely outnumbered by Rosine's demon elves but managed to kill them by lighting himself on fire when they got too close then quickly dousing himself by slicing open the cocoons that were in the process of turning more children into elves. Though not much of a talker, Guts is also shown to possess astute logical reasoning which can be seen in some of his conversations within the manga.
As a youth, Guts lived in a mercenary camp where he was forced to learn to use full sized weapons. This and his natural physical size and strength enabled him to wield larger weapons than most. Throughout the Golden Age arc, he primarily uses a variety of large swords, along with various other weapons when necessary.
In the (chronologically) later arcs, Guts wields the Dragon Slayer, a zweihänder or 2 handed sword about 7' long and 12" wide at its base. It is more than an inch thick at the middle of the blade, giving it incredible weight and power. Described in the manga as more of a table-sized slab of iron than a blade, the Dragon Slayer's massive size makes it the ideal weapon for slaying apostles of the God Hand. After killing many apostles, the sword retains properties of the apostles blood, making it more effective against them. Guts' left forearm is prosthetic with a magnet to help grip weapons, a replacement for the one he lost when Griffith attempted to sacrifice him to the forces of hell; it folds back to expose a hidden cannon within. Guts also carries throwing knives, miniature bombs, a dagger, and even a repeating crossbow that can be mounted onto his prosthetic arm. While not innately magical, Guts's sword, the Dragon Slayer, was recently shown to have become a cursed blade after killing so many Apostles; enabling it to kill creatures of a non-corporeal nature and even harm the members of the God Hand.
One of Guts' most powerful assets is the Berserker Armor, an ancient, cursed suit of armor that allows the wearer to overcome his physical and mental limitations in combat but at the cost of damaging his already-weakened body and allowing his inner Beast, a feral dog-like creature, to take over and endanger everyone in the vicinity, friend or foe (hence, berserk). The Armor has deadly effects on its user. After using the armor once, Guts lost some of his sense of taste, became slightly colorblind, and the stress of using it caused a patch of his hair to turn white, among other things. It can pierce his flesh to reinforce broken bones, enabling him to continue fighting long after his body is broken to the point of exsanguination.
Gutts has incredible strength and physical resistance, even though he is a regular man with no powers. Due to his extensive training since a very young age, his strength and endurance could be classified as superhuman. He is able to use Dragon Slayer remarkably fast, and with just one hand. He has also survived impacts that would kill a regular man, even with the protection of armor.
He also has an incredible resistance to pain as shown when he cuts off his own arm and when he was badly burned.
He is able to come up with strategies very quickly and thanks to his experience in battle he can realize very quickly the best way to fight, like when he used a sword with his feet to impale Zodd.
It has been a matter of some discussion by fans of the series wether or not Guts is entirely human. In addition to his feats of superhuman speed, strength, and resolve, he is the only human character in the series shown to have pronounced canine teeth (fangs) and slightly pointed ears. As Guts is an orphan, born of a corpse on a battle field, his true paternal lineage is currently unrevealed.