The dome was a high end, large-scale resort before it was taken over by the Rattlers at some point and converted into a slave camp for the group. Over the years, they captured many infected and humans alike, with the former chained up and used as guard dogs while the latter are forced into slavery. Those who resist too much are sent to "the pillars", wooden beams set out on the beach where they are strung up and left to die from exposure to the elements.
The Rattlers housed the prisoners in the basement of the resort complex, held behind bars and taken out to work on the farms all day, and beaten if they stepped out of line or refused to work. It was possible to escape the complex; those who do escape are dubbed "runaways" or "strays" that the Rattlers chase to recapture. They purposely harm slaves in a way that wounds them but does not kill them, evidenced by one Rattler stopping another from beating Abby to death with a baseball bat and a patrol leader instructing her squad to shoot runaways in their legs to keep them from running.
Given the fate that awaits those captured, some runaways steal guns to commit suicide. In fact, numerous notes can be found in the area written by residents who either escaped or killed themselves to avoid being captured and enslaved in the dome.
Events of The Last of Us Part II
After Abby Anderson and Lev contacted the Fireflies on Catalina Island by radio, they were ambushed and taken prisoner by a group of Rattlers as they attempted to leave the abandoned Firefly base at 2425 Constance.
A couple of months later, Ellie (searching for Abby) is caught in one of the group's traps. She is found by two Rattlers, the same men who captured Abby and Lev. Hours later, who cut her down and plan to take her back to their base. However, she takes advantage of one Rattler's attempt to scare Ellie by pushing her into a hanging clicker, helping the clicker bite him to death and then takes his gun to shoot the other Rattler in the legs. She then interrogates him for information regarding Abby's location before executing him.
After following a stretch of railroad tracks, she eventually reaches the Rattlers' base, recognizable by a large round building with a domed roof. Sneaking her way in and then fighting through the Rattlers inside, she reaches the cells where the enslaved people are kept. In a brutal fight, she manages to defeat the Rattler guarding the cells and (despite one prisoner wanting to kill her) learns that Abby and Lev attempted to escape to the boats at the beach. The prisoners, finally free, steal several guns from the supply room and then launch an assault on the Rattlers, setting at least one of the complex's buildings ablaze and killing many of them outright in revenge.
- "Santa Barbara"
- The Art of The Last of Us Part II, Naughty Dog and Dark Horse Books, 2020, p.184