The signature wrist-mounted weapon used by Assassins in Assassin's Creed is the Hidden Blade.
The Hidden Blade is a fictional retractable blade worn beneath an Assassin's bracer. In the games, it is designed for concealed attacks and is closely associated with the Assassin Brotherhood. The weapon can be deployed quickly from the wrist, allowing an Assassin to strike without openly drawing a sword or dagger.
The series presents different versions and upgrades of the weapon across historical periods. Altaïr's blade is central to the first game, while later installments add features such as a second blade, poison delivery, and adaptations for characters with different injuries. Leonardo da Vinci modifies Ezio's equipment in Assassin's Creed II.
The weapon is fictional, although the games place it within historical settings and connect it to ritual and Brotherhood traditions. It should not be confused with the Phantom Blade, a ranged wrist weapon introduced in Assassin's Creed Unity, or with ordinary wrist knives used by other characters.