Big Sister

"Mr. B, Mr. B... Big Sister doesn't want you playing with me..."

- Little Sister

The Big Sisters are post-pubescent Little Sisters that have become unstable in Rapture's environment. The Big Sisters wear diving suits reminiscent of those of a Big Daddy's, but they have a distinct aesthetic since they are assembled from scavenged items rather than being manufactured. A Big Sister helmet consists of a large sphere with a single porthole. Big Sisters are formidable beings that are known for their agility and their seven foot tall appearances. They wield huge, wrist-mounted needles on their left arms, which are used primarily for melee attacks and extracting ADAM in a manner similar to a Little Sister's extracting needle. In addition, there appears to be a gun barrel directly above this needle. 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. Ten years after the events of BioShock, they are charged with maintaining the ecological balance in Rapture.

Inevitably, there is an original Big Sister that precedes the others; it is speculated that she might be Eleanor Lamb, the first Little Sister to be bonded with a Big Daddy handler.

There's Something in the Sea
Roughly 10 years after the events of BioShock, the Big Sisters have been traveling to the surface world from Rapture to abduct little girls all over the world. Various individuals started to show interest in the abductions and began an intensive and exhausting investigation. Among these individuals is a man by the name of Mark Meltzer, who began tracking patterns in the abductions. After some planning, Mark attempts to capture a believable photo of the unknown kidnapper. He is unsuccessful, but a Big Sister follows him home and and abducts his daughter, Cindy, the same night. Mark later tries to capture the Big Sister by setting a trap; the plan fails, and Mark is left with a broken leg and four fractured ribs. The Big Sisters continue to abduct children, although Mark persistently tracks them, determined to find his daughter.

BioShock 2
Big Sisters are one of the main enemies in BioShock 2. According to BioShock 2 creative director Jordan Thomas, after the player invokes the wrath of a Big Sister, there will be a set amount of time before she arrives at the player's location. He stated that once she arrives, the player's going to have "the fight of their life".

Strategy
As mentioned previously, there will be a set amount of time before a Big Sister arrives to attack the player. This allows them to rig the environment to their advantage, hacking machinery and laying traps before preparing themselves for the fight. From the videos showcasing a Big Sister in action, they will move very fast from place to place, similarly to a Spider Splicer. A Big Sister's only weapon, besides her Plasmids, is an over-sized needle used to stab targets. As such, movement-impeding plasmids and weapons would be recommended when dueling with them; attacks that do not require precision would also be recommended. It is possible that they might have the same weaknesses as a Big Daddy, although it is yet unclear. They can recharge their health mid-battle by grabbing a wandering Splicer, and quickly draining them with their needle.

Trivia

 * There appears to be a tube located beside a Big Sister's 'needle' which is used for siphoning ADAM out of their victims.

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 La Grande Soeur