In BioShock 2 players will take on the role of the original Big Daddy, not that of game one protagonist, Jack. As a Big Daddy you will have access to all the strengths and weapons of a standard Big Daddy, including the drill and rivet gun. More importantly you also possess free will and the ability to use plasmids and gene tonics — genetic modifications allowed for through ADAM, a stem cell harvested from conquered enemies, or sea slugs outside the Rapture air lock, and powered by the in-game injectable serum known as EVE, which can be found, captured or purchased. Plasmids and gene tonics provide a wide range of aggressive and passive abilities which can be upgraded and arranged for quick use. The ability to use plasmids and tonics gives you a decided edge over other Big Daddies and most other denizens of Rapture, excluding the powerful Big Sisters. In addition, due to their role as a Big Daddy, players will experience a new relation to the Little Sisters. Upon defeating standard Big Daddys you are given the familiar choice as to whether to harvest or adopt them. Harvesting gains you ADAM immediately, but could alter your path through the game, while adopting makes you responsible for Little Sisters, who then accompany you through Rapture, but also provide aid and warning in times of danger. Additional gameplay features include: new plasmids, weapons and the ability to combine these two.