Which Assassin's Creed game first introduced the Hidden Blade's iconic wrist mechanism?

The original Assassin's Creed first introduced the Hidden Blade's iconic wrist mechanism in the game series.

Altaïr uses the concealed blade as his signature assassination weapon during the Third Crusade. The weapon is mounted beneath the forearm and can be extended or retracted, allowing an Assassin to carry it discreetly while moving through crowds and restricted areas.

The first game also establishes the fictional tradition that an Assassin sacrifices a finger to use the early mechanism. Later stories revise and expand that history, showing technological changes that make the weapon safer and easier to operate. Ezio's era, for example, features paired blades and additional tools.

The Hidden Blade is not a literal reconstruction of a documented medieval Assassin weapon. It is a fictional device created for the series' historical-action setting. Players can therefore distinguish the original game's debut of the mechanism from later games that add poison, firearms, or other modifications.