Splicer

Splicers, also known as Aggressors, are the main enemies that Jack encounters over the course of the game. The remains of Rapture's human population, they are the result of a planned attack by Fontaine on New Year's Day of 1959 to end the civil war between him and Ryan. They apparently murdered the sane population. Many of them still wear Masquerade Ball masks, and Atlas asks, "Why do they wear those masks? Maybe there's a part of them that remembers how they used to be, how they used to look. And they're ashamed." Apparently due to the biological weapons attack, they have become biologically dependent on ADAM to survive. Wandering the corridors and the tunnels of Rapture, they search for ADAM, usually in the form of Little Sisters, which often puts them at odds with their Big Daddy protectors—something that Jack can easily exploit to help him survive.

Splicers tend to wear very little armor, if any, but they have advanced physical strength and tend to be extremely aggressive in contrast to the calmer Big Daddies. They will sometimes work in groups, use plasmids and sometimes even play dead to get the advantage on the player.

Splicers can be divided into several separate categories, based on the weapons that they prefer to use.

• Thuggish splicers, who first appear in the Welcome to Rapture level. They attack by rushing the player with melee weapons, such as pipes and wrenches scavenged from the surrounding area.
• Leadhead splicers, who use firearms. They first appear in the Welcome to Rapture level.
• Nitro splicers, who first appear in the Medical Pavilion level and throw explosives such as mines, Molotov cocktails, and makeshift bombs to attack Jack, something that can be exploited with the Telekinesis plasmid.
• Spider splicers, who first appear in Welcome to Rapture however are first combated against in Neptune's Bounty, can crawl on the ceiling and throw hooked blades.
• Houdini splicers can teleport and attack the player with plasmids. They first appear in the Arcadia level.

There are ten splicer models in the game. Their names are not revealed in-game; instead, they are associated with the sound files used for their sound bites in the game data:

• Baby Jane
• Ducky
• Breadwinner
• Waders
• Lady Smith
• Dr. Grossman
• Toasty
• Pigskin
• Rosebud
• White Splicer

BioShock 2

In BioShock 2, the Splicers return as enemies, though much weaker in comparison to their previous role in BioShock (though they have become even more monstrous than in the first game due to years of ADAM withdrawal before Big Sister's arrival)—more than likely because the player will be a Big Daddy. Notably is their limbs have become far more lanky and in some cases their faces have conformed to the shape of their masks. However, in an interview on Gametrailers.com with Jordon Thomas, he mentions that the Splicers have split up into two factions: one representing the "good" ending in BioShock, and the other representing the "bad" ending. The nine Minute Walkthrough has also revealed that you will no longer face one or two at a time because, with the player as a big daddy, that would be a splicer suicide. Instead they will attack in groups. Also should you kill most of them, the final splicer may attempt to flee. Also according to somethinginthesea.com the writer R. Killian Quain was strongly implied to be a former splicer. This indicates some of them have escaped Rapture to the surface. The variations of splicers are still present such as armed splicers and ones that throw grenades. It has also been confirmed that there are new kinds of splicers called Alpha Splicers that are said to be even stronger than Big Daddies.