This sword appears to be utterly unremarkable. It is of curiously colored iron. The construction seems a little clumsy, but a fighter would have no complaints about it.
Several hundred years ago, an evil magician named Hek began terrorizing the land. Attempts to defeat him failed utterly, as did numerous assassination attempts. The only assassin who had escaped with his life relayed that Hek was unaffected by everything the assassin did, including stabbing him in the back repeatedly. (Hek, it seems, found it amusing to allow captured assassins to try to kill him, just before he had them executed.) Hek had discovered immortality. In desperation, a young warrior named Dren went to the local cleric, magician, and swordsmith. Between them, they came up with Magebane, a sword made of cold-forged iron. The peculiar forging techinque resulted in a sword composed of pure anti-magic. Dren went to Hek’s fortress, armed only with Magebane. He walked through all of Hek’s protective enchantments, and eventually killed the magician. Dren was rightly honored as a hero, and when he died, Magebane was buried with him. (A possible adventure is the adventurers finding Drek’s tomb and recovering Magebane.) Magebane is not to be used lightly; it is a very last resort against hellishly powerful magic users.
Magebane is pure antimagic. Spells can’t be cast by anyone in contact with the sword, and any spell/enchantments the sword comes in contact with are instantly nullifed/destroyed. Any magic user that simply touches Magebane will be burned, as if the sword was red-hot. Any magic-users that are wounded with Magebane suffer excrutiating pain, crippling injury, or even instant death (something on the order of quadruple damage). Nonhumans can wield the sword, but it is extrememly uncomfortable for them to hold it for very long. Nonhumans take double damage from it. A magic-using nonhuman will take eight times the normal damage. A person using Magebane will slowly develop a resistance to any and all magic, including beneficial. This effect is permanent, but it stops advancing once the person in question stops carrying Magebane.