Which Assassin's Creed game introduced the grappling hook to the main series?

Assassin's Creed Syndicate introduced the grappling hook to the main Assassin's Creed series.

The grappling hook is used by Jacob and Evie Frye to cross gaps and reach rooftops quickly in Victorian London. It expands the series' traditional parkour system by allowing characters to create rapid zip-line routes between buildings and climb certain structures more directly.

Syndicate was released in 2015 and is set in London during the Industrial Revolution. The city contains districts controlled by rival gangs and institutions, and the Frye twins work to weaken Templar influence while building their own gang, the Rooks.

The device should not be confused with the rope launcher in Assassin's Creed III. That earlier tool was designed for climbing trees and other environmental traversal, whereas Syndicate's grappling hook is a powered urban traversal gadget built into the protagonists' equipment.