You are Subject Delta, a prototype ‘Big Daddy’ created in Ryan Industries’ Protector/Gatherer program. The original Big Daddy prototypes (called the Alpha Series) were leaner and more agile than the mass-produced models that came later, and each was bonded to a single Little Sister.
You were apprehended after discovering Rapture during a diving expedition. Knowing they couldn’t release you back to the surface to reveal the secrets of Rapture, you were “volunteered” as a subject for the experimental program. You were the first Big Daddy successfully pair-bonded to a ‘Little Sister,’ designed to protect her—and only her—with your life.
Now, unlike your fellows, your freedom of will has been mysteriously restored.
In Rapture, you are something entirely unique.