Abyss Greatsword

The Abyss Greatsword is a Boss Soul Weapon in Dark Souls. It is obtained by ascending a +10 sword with the Soul of Artorias. Alternatively, it can also be created by enhancing a Parrying Dagger to +10, and ascending that.

In-Game Description
This greatsword belonged to Lord Gwyn's Knight Artorias, who fell to the abyss.

Swallowed by the Dark with its master, this sword is tainted by the abyss, and now its strength reflects its wielder's humanity.