The player will take the role of the first Big Daddy ever created in Rapture, who has seemingly survived the events of the first game. As such, the Big Daddy's drill and rivet gun will be weapons that the player may use, but will overheat if used constantly. Alternatively, the player may also use plasmids, and their effects have been changed, while "upgrade trees" will provide unique ways to upgrade plasmids. Further Big Daddy abilities found in the first game, such as performing a body slam, will also be an option.[2] The Big Sister also appears to be a very serious threat to the player. When a certain amount of Big Daddies are killed she will attack. Unlike the Big Daddies, she is lightning quick and arguably more powerful.
As a "rogue" Big Daddy, players will attempt to capture the Little Sisters from other Big Daddies who roam Rapture. Once caught, the player will again have the option of choosing the fate of the Little Sisters. Harvesting remains a possibility in order to gain more ADAM, but rather than rescuing the Little Sister, players will instead be allowed to adopt them. With this option, Little Sisters will ride around with the player's Big Daddy, and will look for ADAM to harvest from corpses; in a manner similar to the final area of the first game, the player will then need to ensure that splicers will not harm the Little Sister as the harvesting process takes place. Rescuing, while not initially an option for the player, will become available at some point in the game.[2] Additionally the Little Sisters will also warn the player when the Big Sister is approaching by singing a tune.
Returning features from the first game include Vita-Chambers to allow the player to regenerate, and audio diaries. In addition to the single-player story, online multiplayer will be a feature in BioShock 2.[2]
