Berserker, as Hyde, has an appearance similar to a werewolf with black fur covering his body, a large jaw, sharp fangs, and a beast-like, humanoid form. His eyes glow upon seeing the full moon.
As Jekyll, he is shown to be fancily dressed in a white dress shirt, an olive green vest, and a black and grey jacket draped across his shoulders. He wears a black and white handkerchif with a red jewel around his neck, and leather gloves over his hands.
His Noble Phantasm is Dangerous Game, the transformation elixir, which allows him to turn into Mr. Hyde, the second personality inside his body that claimed so many victims in his life. Upon drinking it, his form changes, becoming covered in black fur, his spine cracking, his muscles expanding and growing long canines and sharp claws and his eyes becoming blood red, making him somewhat similar in appearance to a werewolf. In this form, his stamina greatly increases, as well as his strength and speed. He gains several skills that make him suitable for close quarters combat, most noticeably, a skill that he calls "Restructuring", which grants him a high enough recovery ability, so that he is confident that he can recover even from being hit by a Noble Phantasm.
He shows himself able to endure Caster's heavily layered defenses and break into his Bounded Field, but he only is able to fight Saber for a small amount of time since he is being burdened by the barrier and because his master is inexperienced.
He also proves himself worthy of his boast regarding his recovery ability, as even with his Master dead and not possessing any form of Independent Action, he is able to survive for a sizable amount of time even while facing Archer, Lancer and Saber at the same time and being wounded by them several times. Even after he is hit by a beam of light by Rider, he still has enough strength left to attack Saber, requiring the swordsman to stab him through the heart before he is ultimately brought down.