Barring some enchantment, steel is the strongest metal alloy available for the construction of weapons. The crafting of steel requires iron and Steelfire, a peculiar additive made from Tar and Brimstone.
The smiths of Akbitana in Shem are the finest in the world and a weapon made of Akbitanan steel is considered to be unbreakable. Due to their great demand, it is rare to find a Akbitanan weapon outside of Shem.