Item from Berserk by Kentaro Miura
Too big to be called a sword — a slab of iron forged to kill dragons that found its purpose killing things far worse, tempered by the malice of every demon it has ever slain.
The Dragon Slayer is Berserk's most iconic object — a weapon that shouldn't work, wielded by a man who shouldn't be alive, against enemies that shouldn't be killable. Godot forged it when a lord demanded a sword that could slay a dragon. The lord called it crude and impractical. Godot fled with it. It sat in his forge for decades until Guts picked it up during an apostle fight and realized it was exactly what he needed. Years of slaying demons, apostles, evil spirits, and astral beings have tempered the blade with accumulated malice — it now exists partially in the astral plane, allowing it to wound beings that normal weapons cannot touch. It can damage God Hand members. It cracked Grunbeld's corundum skin. It wounded Slan. In Guts' hands, amplified by the Berserker Armor, it becomes the most dangerous weapon in the world. It is also, functionally, Guts' identity. The Black Swordsman is the man with the impossible sword. You see the Dragon Slayer before you see the man carrying it.
An enormous blade of rough iron, wider than a man's torso and longer than most people are tall. It looks less like a weapon and more like a sharpened tombstone. Its surface is scarred and pitted from countless battles against supernatural beings. It functions as both sword and shield — its width can block attacks that would pass any normal guard. The weight is staggering; two trained knights struggle to lift it, but Guts swings it one-handed.
Also known as: The Dragonslayer, Guts' Sword