You already know the Little Sisters from the first BioShock. They are practically invincible little girls, with ADAM slugs placed inside their bodies. They see the world in a different, more colourful way and their only task is to collect the precious substance. Each Sister is protected by a Big Daddy, who's only goal is to defend his little companion. Locations of some of the girls may differ from the ones marked on the map. The reason for that is the fact that they move around the city and appear randomly. However, if there are 3 Sisters on a level, you will meet all of them sooner or later, in one place or another.
The substance they are collecting is the main "currency" in Rapture - the key to gain new Tonics, Plasmids or increase health of EVE. There are various ways of obtaining ADAM:
1. After getting rid of a Daddy, you can adopt the Sister, or harvest her on the spot (160 ADAM). Doing so is highly inadvisable, as each of them can collect additional ADAM from two bodies marked on the map (you get 40 for each or 60 if you have the [Proud Parent] Tonic equipped). After harvesting both bodies, head to a vent, where once again you will have to decide about the Sister's faith - rescuing her will give you 80 ADAM, while harvesting is worth 160. As you can see, you waste 120 ADAM by harvesting the Sister immediately.
2. Each time you take care (in one way or another) of every Sister on a level, the Big Sister will appear. Search her body to find 40 ADAM.
3. At some moments in the game, you will get to move around the depth of the ocean. While you're there, search for slimes, as each gives you 10 ADAM.
NOTICE: A throughout description of Big Sister and Daddy behaviours and fighting tactics can be found in the proper chapter of this guide.
NOTICE 2: The ways you treat the girls has a decisive influence of the ending of the game. Hack out the "Possible endings" chapter for more info.
If you decide to rescue the girls, you'll receive a present for each 4 Sisters - there will be a teddy bear by the nearest Gatherer's Garden. There are 12 Sisters in total, so you can receive 3 presents:
- [Proud Parent] Tonic, 80$, 80 ADAM
- [Demanding Father] Tonic, 160$, 120 ADAM
- 160$, 250 ADAM
If you decide to adopt a Sister, she can guide you to the nearest body (and then a vent) if you press and hold [R]. It will cause a white stream to appear and guide you to and Angel. You can also use the included level maps, on which I've marked each body and vent.
During the harvest, you'll be constantly attacked by enemies, who will appear from every possible direction. That's why you should choose those bodies, which are the easiest to defend. The room shouldn't have many entrances and, if it's possible - no balconies, so enemies can't appear from above. Below I've pointed out the things which will make your fight easier. Of course you don't have to fulfill all of them, but each one makes the fight lighter.
1. If there is a Bot Shutdown panel nearby, cause an alarm and hack 2 bots.
2. Stock up on ammo, hack all nearby machines.
3. Place traps by each entrance (trap rivets and spears, mines, [Cyclone Trap] - level two or above works best).
4. Set mini-turrets and traps around the girl herself.
5. Use Hypnosis during the fight.
6. You can freely use the more powerful weapons like the [Gatling Gun] and [Launcher], you won't harm the girl anyway.