Sword of Eden #1, cataloged by Abstergo Industries as Piece of Eden 25, was one of the Swords of Eden, sword-like artifacts created by the First Civilization scientist, Hephaestus, to fight during the War of Unification. These Pieces of Eden seemed to grant their bearers great power and leadership, and were later used by influential humans in battle.
This particular Sword was long thought to have been damaged during the French Revolution, but Professor Simon Hathaway, a Templar historian who was in the process of exploring the memories of his ancestor Gabriel Laxart in 2016, discovered that the Sword had been missing a vital component that had prevented it from functioning fully since the Hundred Years' War.
The Sword of Eden was created by Hephaestus, "the maker", during the Isu Era to bring about the end of the War of Unification. Although effective in its own right, the weapon was designed to work in sync with a spherical, scarlet Piece of Eden known as the Heart which sat inside the Sword's pommel.
By the early 14th century, the Sword was in possession of the Knights Templar. In 1307, the Templars were branded heretics by Pope Clement V, with their base, the Parisian Temple, subsequently being attacked by King Philip the Fair's forces. During this assault, Grand Master Jacques de Molay entrusted his advisor with hiding the Sword.
The advisor obliged, concealing the Sword along with de Molay's codex within a secret underground chamber, but was killed shortly thereafter by Thomas de Carneillon. De Molay, however, had removed the Heart from the blade and, while in prison awaiting execution, buried it away within some graffiti on the wall of the cell.
In 1794, during the French Revolution, the Sword hidden in the Parisian Temple was acquired by François-Thomas Germain, who used the Sword during his fight with Arno Dorian and Élise de la Serre. The Piece of Eden granted the Grand Master extraordinary abilities, such as teleportation and deadly energy blasts. However, in a reckless flurry of attacks, Élise struck a blow to the Sword which destabilized its power source.
When Germain attempted to retaliate with another energy blast, the Sword malfunctioned, with the subsequent explosion demolishing much of the Temple, killing Élise and mortally wounding Germain himself. Following the event, the weapon ended up in Arno's possession; while it no longer possessed its former powers on account of the damage it sustained during Élise's attack, the Sword remained as one of the most powerful weapons in Arno's arsenal.
- The Sword is unique in that it is the only Piece of Eden that can be kept and actively used by the main character after the game ends. The Apples of Eden are sealed away, the Staff disappears and the Shroud is returned to its resting place.