In Dark Souls, the Lordvessel is placed at Firelink Shrine’s altar to open the paths to the Lord Souls.
The player receives the Lordvessel after defeating Dragon Slayer Ornstein and Executioner Smough in Anor Londo and meeting Gwynevere. It is a major progression item because it changes the purpose of Firelink Shrine and allows the chosen “kindler of the flame” to continue the main quest.
After obtaining it, the player can bring it to the altar beneath Firelink Shrine. Depending on the route chosen, Frampt or Kaathe can guide the player through the process. Once the Lordvessel is placed, several previously inaccessible areas become central destinations: the Duke’s Archives, Lost Izalith, the Tomb of the Giants, and New Londo Ruins. The Lordvessel is sometimes confused with the Lord Souls themselves. It does not contain the four Lord Souls; it is the vessel used to gather them and open the way to the Kiln.