Jacob is the first name of the Assassin's Creed Syndicate twin who leads the Rooks.
Jacob Frye and his twin sister Evie Frye are the game's two principal protagonists. In Victorian London, Jacob creates the Rooks, a street gang that opposes Templar influence and helps the Assassins challenge criminal and political control of the city.
Jacob is generally associated with direct action, gang recruitment, and taking territory from rival groups. Evie places greater emphasis on stealth, investigation, and recovering an Isu artifact. Players can switch between the twins during much of the campaign, while certain missions are assigned to a specific sibling.
The Rooks are therefore linked to Jacob's campaign, not to Henry Green, the London Assassin who assists the twins. Lydia Frye, Jacob's granddaughter, appears in a separate World War I sequence rather than leading the Victorian gang.