The Greatsword of Artorias can be created by ascending a Straight Sword Hilt +10 or a Broken Straight Sword +10 at the Giant Blacksmith in Anor Londo, with the Soul of Sif and 5,000 souls. Using the Soul of Sif with any other straight sword, greatsword, ultra greatsword or dagger, will create the Cursed variant.
The Greatsword of Artorias has the potential for very high damage. However, since its scaling is spread so much throughout the stats, it is hard for specialized builds to capitalize on much of the potential scaling. If the player has 40 Strength, Dexterity, Intelligence and Faith, the Greatsword of Artorias has a total Attack Rating of 658, 348 of which is physical and 310 magical. This means it has the highest Attack Rating with these stats, when one-handing the weapon. However, at 50 Strength, it is outdamaged by Grant. Note, that since both weapons’ Attack Rating consists of a split between physical and magical damage they will be inferior to a weapon with only one damage type of similar strength. It boasts the strongest Divine modifier of any weapon, however, and as such, it is able to grossly outdamage the Grant against specific foes, although this is only relevant in PvE. The Greatsword of Artorias also has a unique 20% damage modifier against the “servants of dark”. These include Darkwraiths, the Four Kings, and Kirk, Knight of Thorns.