The game will be set in 19th century London, during the Victorian era, with twin protagonists, Jacob and Evie Frye, both of whom are playable. The two arrive in London in 1868, as the Industrial Revolution reaches its climax, bringing its lot of inequality and poverty in a city controlled by the Templars. To stop their rule, the Fryes will take over the organized crime in an effort to gather an army and free London.

Much like in Diablo and Diablo II, equipment is randomized. In addition to base stats (such as damage and attack speed for weapon or armor points on armor), higher-quality items have additional properties, such as extra damage, attribute bonuses, bonuses to critical hit chance or sockets (which allow items to be upgraded and customized by adding gems for various stat bonuses). Magic-quality items have 1 to 3 random properties, rare-quality items have 4 to 6 random properties and legendary-quality items typically have 6 to 8 properties with varying degrees of randomness (for example, the Mempo of Twilight, a legendary helm, always has a socket, bonuses to elemental resistance, attack speed and life, a bonus to either Intelligence, Dexterity or Strength, and one additional random property, however the magnitude of these bonuses varies from item to item), and set items are a subtype of legendary items which provide additional, cumulative bonuses