Folding Blade

The Folding Blade is a unique sword and the primary right-hand weapon for Corvo Attano and Emily Kaldwin in most of Dishonored and Dishonored 2. The only gameplay difference between this and other swords is that it can be upgraded.

Description
The blade's mechanism is resilient and efficient for both stealthy assassinations and open melee combat. It is comprised of several segments that collapse into each other much like a spyglass, thus it can fit inside of the handle entirely. This utility combined with its dense metal makes it perfect for defensive maneuvers. It can be upgraded by Piero Joplin or black market shops to be more effective at "locking blades" and pushing away enemies. In Dishonored 2, the sword also has two Masterwork upgrades, allowing it to kill either Clockwork Soldiers or witches much faster.

History
The Folding Blade was invented and crafted by Piero for Corvo Attano during the Rat Plague, to help him carry out assassinations for the Loyalist Conspiracy. Loyalist supporters stashed it with the crossbow in the sewers for Corvo's escape from Coldridge Prison. Later in the Flooded District, Daud throws away the sword along with the rest of Corvo's equipment, which he can choose to take back at the Greaves Refinery.

In the years following the end of the plague, Corvo continued to use it for in his duties as Royal Protector and Royal Spymaster. Fifteen years later, felon Watch Captain Mortimer Ramsey steals the sword during Delilah Copperspoon's Coup at Dunwall Tower. He stabs Lieutenant Alexi Mayhew with it in the Royal Chambers before throwing it away. Mayhew stays alive long enough to give the Folding Blade to the protagonist, who keeps it with them on the rest of their journey.

After Delilah was defeated and Emily restored to the throne, another blade was made. When the Rat Gang emerged and intended to sow chaos in Dunwall, both Emily and Corvo can be seen wielding their own blade during their mission to eradicate the new threat.

Dishonored

 * Whirlwind I - Swing speed for swords is slightly faster.
 * Whirlwind II - Swing speed for swords is moderately faster.
 * Fencer - Advantage in sword vs. sword combat.
 * Fleet Fighter - Drawn weapons do not slow movement speed.

Dishonored 2

 * Fencer - Win locked-sword Contests more easily.
 * Whirlwind - Sword attack speed is slightly faster.
 * Power Slash - You deal greater damage with your sword, but your sword attacks are slower.
 * Risky Parry - During melee combat, your sword parry always knocks an enemy down, but you take damage when parrying.
 * Leech Cuts - You gain Health when inflicting sword damage or assassinating enemies.
 * Fleet Fighter - Drawn weapons do not slow movement speed.

Trivia

 * The blade will take on an appearance indicative of mineral ore in the amalgamation of the blade's metal if the sword crossing upgrade is purchased.
 * During development, the Masterwork upgrade Monkey Wrench was called The Grinding Blade.
 * In the mission, The Flooded District, Daud does not flip the hilt to make the blade come out, as opposed to Corvo's usual method.
 * In The Art of Dishonored 2, Corvo's blade is called "Pathmaker".
 * Doppelgängers with the Deadly Shade upgrade have a copy of the Folding Blade. This sword disappears when the Doppelgänger does, and does not appear to be affected by upgrades.
 * With the supernatural ability Reflexes, Corvo and Emily can use the sword to intercept projectiles. With the appropriate upgrades, these projectiles can be deflected towards the nearest enemy and the time window for successful parrying increased.
 * Retrieving the Folding Blade along with the rest of Corvo's gear from the Greaves Refinery will unlock the Dishonored achievement This is Mine.
 * The Dishonored 2 achievement Fatal Redirect is achieved by using the Folding Blade to deflect a projectile back at the protagonist's enemies. This requires the Superior Deflection upgrade for the Reflexes supernatural ability.