Jacob Frye founded and led the Rooks gang in Assassin’s Creed Syndicate.
Syndicate, released in 2015, is set in London during the Industrial Revolution. Twin Assassins Jacob and Evie Frye arrive in the city and oppose Templar control over its institutions, businesses, and criminal networks. Jacob creates the Rooks as a street gang allied with the Assassins and uses them to challenge the rival Blighters.
Jacob is more openly aggressive and interested in building influence through direct action, while Evie is generally more focused on stealth, investigation, and recovering an Isu artifact. Players can switch between the twins during much of the campaign, and each has distinct abilities and equipment.
Evie is therefore the main alternative answer, but she does not found the Rooks. Henry Green is a London-based Assassin who assists the twins, and Maxwell Roth leads the Blighters before becoming Jacob’s enemy.