The treaty is an item a player receives when they present Queen Sigrid with the Good anthem during the Throne of Miscellania quest. Players need to take it to King Vargas for his signature, where they will discover that he can't hold a normal pen due to his affliction. King Vargas will take the treaty from the player while they construct a Giant pen. Players cannot get it back after this point.
Originally players doing the quest were given a Letter containing the peace treaty instead of the treaty itself.