Which Assassin's Creed game introduced the grappling hook for its London setting?

Assassin's Creed Syndicate introduced the grappling hook for its London setting.

The grappling hook is a traversal tool added in Syndicate, the 2015 game set in Victorian London. It lets Jacob and Evie Frye quickly reach rooftops, cross gaps, and ascend tall buildings, reducing the time needed to climb the increasingly vertical city.

Its inclusion reflects the game's industrial setting. London contains wide streets, railway infrastructure, factories, and large buildings that can be traversed more quickly with a mechanical launcher and rope. The tool also supports stealth approaches by giving players new ways to enter or leave an area.

The grappling hook is not the same as the rope launcher in later discussions of the series, and it should not be confused with the ship-based tools in Black Flag or Rogue. Syndicate is the entry most specifically associated with this urban grappling device.