Subject Delta

"I had thought you some golem of Sinclair, brought here to hold Rapture's arms as he rifles through her pockets. But no... you are aware of your plight. Who I wonder would be so cruel? To force a mirror on a man with no face..."

- Sofia Lamb

Subject Delta (Symbol: Δ) is the protagonist of BioShock 2. Delta was the first successful Big Daddy subject bonded to a Little Sister. He has a Delta symbol on his suit. Delta is the fourth letter in the Greek alphabet, signifying that Delta was the fourth test subject taken from Persephone for Alpha Series conversion at Fontaine Futuristics. Delta is also a symbol commonly used in mathematics to represent change or variation.

Features
Subject Delta has the features of a Big Daddy, such as the vocal cord modulator surgery and large diving suit. Like all Alpha Series Big Daddies, he retains a large degree of free will, but he is forced into a protection bond with a single Little Sister. As a prototype, Delta is granted use of the Bouncer's Drill (which is detachable and goes over the hand), in addition to other weapons, such as the Rosie's Rivet Gun, and a Hack Tool that allows him to remotely hack from a distance. He also has the ability to use Plasmids, and can wield them simultaneously with his weapons. Delta's suit was designed specifically to allow the efficient use of Plasmids. His gloves have openings on his fingertips and palms to accommodate the necessary contact with the environment projectile Plasmids need, his sleeves have IV ports for ADAM injection and a tube for transporting EVE from his tank straight to his wrists to allow swift replenishment even during combat. Being less bulky than the production models gives Delta greater speed and agility than other Big Daddies, at the sacrifice of some of the raw strength and endurance they possess. Also, First Aid Kits and EVE are fed intravenously to Delta, meaning he can continue fighting while replenishing his EVE reserves. A camera attached to the top of Subject Delta's helmet allows his allies to watch from his perspective and keep track of his progress through Rapture.

Throughout the game Delta must defeat other Big Daddies and take their Little Sisters, at which point he is given the option to either "harvest" or "adopt" them. Harvesting functions the same as it did in BioShock, whereas with the new "adopt" option, Delta puts the Little Sister on his shoulders, forming a temporary bond with the girl. He protects her as she extracts ADAM, and the Little Sister will give him some of the ADAM she harvests from Splicer corpses as a reward. After she has finished, Delta can send her to a Little Sister Vent, where he will have the final choice of saving or harvesting the Little Sister.

History
Before his arrival in Rapture, the man who would become Subject Delta was a deep sea diver who conducted an investigation of the many ship and submarine disappearances in the Atlantic Ocean southwest of Iceland. While surveying the area in an advanced diving chamber, he accidentally discovered the hidden city. He was accepted into Rapture, becoming something of a celebrity for his heroics and nicknamed "Johnny Topside" by articles in the Rapture Tribune.

Stanley Poole, a journalist, had written a story on "Johnny Topside" and brought it to Ryan's attention. Ryan did not trust the visitor's story and was convinced that he must be a government agent sent to spy on Rapture. Ryan had him incarcerated at Persephone Penal Colony. Thus, he effectively disappeared from the public eye, put with exiled citizens who had worked against Ryan's philosphy and endangered Rapture.

As a prisoner in Persephone, he was contracted out by Augustus Sinclair as a test subject for research of Adam products. He was labeled "Subject Delta" (Δ) and was transferred to Fontaine Futuristics to be used in various Plasmid experiments, performing in the Plasmid Theater to amaze crowds of  Rapture citizens. Eventually, he became one of the candidates for conversion into a Big Daddy. He endured strenuous genetic and physiological conditioning, losing much of his free will in the process, and became the first Alpha Series protector to successfully bond to a Little Sister. His bond partner was Eleanor Lamb, the daughter of Rapture's psychiatrist Sofia Lamb, who had been incarcerated in Persephone not long before.

At some point during New Year's Eve of 1958, Eleanor and Delta began their normal rounds of harvesting ADAM. Eleanor was attacked by four Splicers, and as Delta fought to protect her, one of the Splicers used the newly-developed Hypnotize Plasmid on him. The Splicers were Sofia Lamb's agents, and Lamb herself used the Hypnotize's effect to force Delta to kill himself in front of Eleanor, using a point-blank shot to the head with a Luger pistol.

BioShock 2
As Eleanor grew up in her mother's care, she still remembered her "Father," Delta, and longed for a way to bring him back. Through her influence over the other Little Sisters, she managed to find Delta's body and extract a gene sample. She used this sample to calibrate the Vita-Chambers to his genetic frequency. She also contacted Brigid Tenenbaum, requesting her aid in undoing the psychological conditioning that had been imprinted in Delta's mind when he was a Big Daddy. Roughly ten years after his death, Eleanor's plan succeeded in bringing her "Father" back.

Subject Delta is revived in a Vita-Chamber in the  Adonis Luxury Resort. Having no recollection of the previous ten years, Delta is unaware of his surroundings and has no knowledge of the downfall of Rapture. He is greeted by a distorted radio transmission from Brigid Tenenbaum, and receives a strange vision of a girl's face with the word "Father" when he finds a gift of the Electro Bolt Plasmid. He returns power to the broken generator in the level to open a door and Tenenbaum speaks to him more clearly, promising to tell him what she knows of his past if he will travel to meet her in the ticket booth of the station in the Atlantic Express train yard. Delta meets a Big Sister who destroys a window forcing Delta to walk through the sea.

Delta begins his journey to her, but is assaulted by Splicers loyal to The Rapture Family in a trap laid for him by Sofia Lamb. He survives, but Lamb continues to follow his progress through the city, contacting him through the radio and calling Splicers to attack him. Eventually, he reaches Tenenbaum who has several Little Sisters with her. She briefly tells him of the situation in the city and what little she knows of his own background. Tenenbaum tells him to find Augustus Sinclair and follow his instructions to reach Fontaine Futuristics to find his bonded Little Sister, Eleanor. She escapes while Delta takes on a wave of attacking Splicers.

Subject Delta meets up with Sinclair in the train station of Ryan Amusements and uses a newly obtained plasmid Incinerate! to clear the ice blocking the train to continue on to Pauper's Drop. There he is trapped by a city-wide lockdown initiated by Lamb, and forced to find Grace Holloway in The Sinclair Deluxe tenements to get the security key from her. As he makes his way through Rapture's poor district towards Grace's apartment, Delta learns more about her history with Eleanor and why Grace holds such a strong grudge against Delta. When they finally meet face to face, Delta has the choice of whether to kill Grace or show mercy by letting her live.

After he obtains the key from Grace, Delta and Sinclair continue in the Atlantic Express train on their way to Dionysus Park. However, as they approach the Park the train is hit by a torpedo launched by Simon Wales in Siren Alley. Delta is thrown from the train car and lands on the ocean floor, while Sinclair continues on to Dionysus in the damaged craft. Dionysus Park was long ago flooded, and Delta must hurry to drain it using the pumping station in Siren Alley before oxygen runs out in Sinclair's train car. However, the pumping station is heavily guarded by Simon Wales and loyal Splicers of The Rapture Family. After Delta defeats them, he accesses the pumping station and drains all the water from Dionysus. Sofia Lamb floods Siren Alley to demonstrate how little regard she has for others lives. Delta then, walks through the flooding Siren Alley, onto the seafloor and into  Dionysus Park.

In Dionysus, Delta meets Stanley Poole, a spy for Ryan who was instrumental in Ryan's arrest of Sofia Lamb. Stanley is locked in the security booth of the train station and refuses to let the train pass until Delta has dealt with every single Little Sister in the level. After Delta dealt with each Little Sister, Eleanor Lamb tells him about the memories hidden in the harvested ADAM which Stanley had not wanted to be discovered. Delta learns that Stanley was the one who flooded the entire park, killing all the people inside, and was the one who handed Eleanor over to be made into a Little Sister. He also learns that Stanley gave Delta to Ryan to be put in prison. Stanley opens the way for the train to leave, but Sofia Lamb unlocks the train booth, giving Delta the choice of whether to take revenge on him or leave him.

From Dionysus, Atlantic Express moves to Fontaine Futuristics, their destination. Delta hopes to find Eleanor here, but she is actually in Persephone, which can only be accessed by getting a genetic key from Gilbert Alexander. Alexander has gone insane, but left messages from before his insanity for anyone who would come in the future to end his life. Following his instructions, Delta enters the hidden labs of Fontaine Futuristics and sees what Sofia Lamb's philosophies have caused Alexander to become. Delta takes the genetic sample for the key from Alexander and his pre-insanity recording urges Delta to end his life.

Delta finally finds Eleanor in the Persephone Detention facility. However, she is sealed in a decontamination chamber. In an effort to kill him once and for all, Sofia Lamb suffocates Eleanor to stop her heart just long enough to break Delta's bond with her and begin his own death. Sofia's plot succeeds, but, with Eleanor's help, Delta is freed and works with Eleanor to try to escape in a submersible owned by Augustus Sinclair. In response to this, Sofia orders her loyal followers to detonate various charges around the overhanging complex of Fontaine Futuristics and Persephone, dropping the entire structure into a trench below. Eleanor, using the powers she had gained from the ADAM injection treatments her mother forced on her, teleports herself to the rising escape submersible just as the charges detonate. She reaches out and attempts to teleport Delta as well, but the explosives detonate before he gets close enough to grab her hand. However, Delta is close enough to the submersible to grab onto a railing on the outside and climb onto it as it rises towards the surface.

Ending
Delta is able to survive long enough to reach the surface with Eleanor. However, Delta's wounds and shattered bond with Eleanor become too great a burden for him, and by the time he and Eleanor reach the surface, he is breathing his dying breaths. Depending on the players choices throughout the game, one of two outcomes are possible. In the end, Eleanor either preserves Delta's essence within herself by extracting his ADAM, or she allows him to die.

Trivia

 * An early preview video of BioShock 2, "Hunting the Big Sister" showed Delta's reflection when he first awakened to be the same model as a Rosie. This was a preliminary model before the Alpha Series designs were finalized.
 * Despite having a helmet on, Subject Delta can still eat and drink.
 * Subject Delta and Subject Sigma are the only Big Daddies seen with the ability to take off their helmets (although the player is unable to see their faces). While this may be common to all Alpha Series, no others have been seen doing so to date. Production model Big Daddies (e.g. Rosies, Bouncers, and Rumblers) were created by grafting their organs into their suits, making helmet removal seemingly impossible.
 * Jordan Thomas, Director of BioShock 2 revealed that in a preliminary plan for the plot of BioShock 2 had "Meltzer tracking the player's investigative trail, realizing he was a kindred spirit, but it got convoluted so we kept it more open."
 * The lack of a true name for Subject Delta was a deliberate choice by the game developers. They felt that giving him a name would only add more distance between the player and the experience of being the character
 * A removed "Eleanor vision" that is still present in the game files reveals that (at one point) the developers had intended Subject Delta to be Eleanor's actual biological father. The file name is "VO_ABY_S_Bsis_Pairbond_03a". A second file shows they also planned to make it clear she was not Delta's daughter "VO_EDN_R_BSis_PlrPlyAsLS_13b"
 * In one of the original concepts for what would become Subject Delta, his armor would have been painted to resemble WWII bombers. As quoted by Colin Fix, Senior Character Concept Artist, 2K Marin, in the Deco Devolution artbook, "I really focused on old WWII bombers for the look. If you came around a corner and saw this guy, you would think 'this is a bad ass Big Daddy that's going to kill me.' " It had a classic shark face across the stomach, "DF 2-22" on the shoulder, and a representation of a blond woman in a flowing red dress on the forearm.
 * The Little Sisters almost never call Delta "Mr. B./Mr. Bubbles," including his bonded Little Sister Eleanor, who only ever addresses Delta as "Father" and, when she was young, "Daddy".
 * In a security photo labeled "Shoot On Sight" seen on TV screens in the game, Delta appears to be holding a Rosie's Rivet Gun and not the one the player receives in the game. In another, labeled "Interloper," Delta appears to be holding the Rivet Gun he actually uses in the same manner as the Rosie's Rivet Gun shown in the "Shoot On Sight" photo.
 * During the sequence where the player controls a Little Sister in Outer Persephone, Delta's armor is colored gold and white, while the symbol on his hand is colored in jade. This is due to the Little Sister's mental conditioning, which allows her to see Rapture in an a much cleaner way, hence Delta looking more "colorful." Little Sisters may see all Big Daddies like this.
 * Subject Delta, along with Subject Sigma, are the only known Alpha Series to use a Drill.
 * Subject Delta is mentioned in "BioShock: Rapture," both as his former self and his Alpha self.