In BioShock 2, the Big Sisters are post-pubescent Little Sisters that have become unstable in Rapture's environment. Ten years after the events of BioShock, they are charged with maintaining the ecological balance in Rapture. The Big Sisters' designs are geared towards accommodating Little Sisters; they have a cage-like basket that is adorned with ribbons, which is used to safely carry Little Sisters on their backs, and childish doodles can be seen on their oxygen tanks.
