"Like a hunted animal, a wounded Barbarian jumps from his hiding place and attacks you. He is angry and determined to fight to the death, and there is no time to explain that you mean him no harm. When the battle is over, you bury him, keeping his Greatsword for your trouble."
The Greatsword is an artifact from Heroes of Might and Magic IV, giving heroes +13 melee Attack. It uses both hand slots.
The Greatsword is a wonderful item, greatly enhancing a hero's ability to damage. Due to it's early game nature, a Greatsword can easily double the damage output of a fighter, since heroes start with low Attack ratings.
It's downside is the fact that wielding a Greatsword uses both the Right and the Left Hand slots, making it impossible to a hero to wear a shield in the same time (shields can only be worn in the Left Hand slot). Besides, it's pricey too.