The primary function of the Berserker Armor, by way of its od, is to suppress the physiological and subconscious systems of the human body which would normally prevent a person from exerting enough force to injure themselves. The result is a significant augmentation of the wearer's physicality, increasing strength and speed to previously unimaginable levels. The armor does this by eliminating the distress caused by pain; the wearer can still feel pain as a sensation, but the mind does not interpret the pain as being a problem, allowing for it to simply be ignored. It also invokes a tremendous bloodlust in the wearer, amplifying negative emotions like hate, fear, and anger that enable the wearer to fight harder. The armor also temporarily repairs debilitating injuries in the heat of battle. For instance, a broken arm will be pieced together by the armor injecting thin spines from itself into the broken bones, returning them to their proper places and restoring the limb's functionality. Additionally, Guts noted whilst venturing into the Sea God abode that the activated armor enhances his night vision. The armor can also repair itself if damaged.
Upon inducing a berserker rage, the armor's helm takes on a distinct appearance. In Guts' case, the helmet and bevor are shaped like the Beast of Darkness; able to function as a mouth capable of biting enemies. When the armor is active, the helm's eye sockets glow red and Guts' face is completely obstructed; if in control of himself, however, the swordsman's face is partially visible and the helm's eye sockets stop emitting their red glow, instead showing his real eye.
In one instance, the Berserker Armor has displayed the ability to impart unto its current wearer a "blood memory" seeped into it of a previous wearer's final moments.