(Covers information from Anderson's universe)
Rain Ocampo was a member of an Umbrella special forces commando unit. During the outbreak in Hive, she and the other operatives were sent down into the underground facility to contain the T-Virus infection. Rain was later cloned for experimentation by the Red Queen.
She was the group's most skilled marksman, and had at least one close friend in J.D. Salinas. She did not like Chad Kaplan, the only member of the group who had never seen action, and grew to blame him for the deaths caused by the Red Queen when he thought she had no more defensive abilities.
She, Matt Addison, and J.D. encountered the first Undead, who they thought was a crazed survivor. The infected woman attacked Rain, and Rain was bitten savagely on the hand, thus becoming infected with the T-Virus. J.D. shot the woman several times but scored no headshots, leaving the Undead still standing until Rain blew it away with a burst from her MP5K. J.D. remarked in shock how the woman could remain standing after he shot her five times, to which Rain responded that she wasn't standing anymore. Both were further shocked to discover her gone despite being shot innumerable times, but she then jumped out to attack Rain again. Permanently dropping the Undead with a neck breaker, Rain, J.D., Kaplan and Matt Addison were attacked by a horde of Undead while waiting for their teammates. She sustained more bites over the course of the survivors' escape from the Hive, speeding up the rate of infection.
At the brink of leaving the Hive and eventually discovering Spence's betrayal and death, they were forced to restart the Red Queen in the hopes that she would provide them with the information necessary to escape. The Red Queen promised to provide them with the four-digit access code only on the condition that Alice would kill Rain, which would keep the infection from escaping the Hive.
The Queen conjectured that the time elapsed since Rain's infection would drastically lessen the effectiveness of the serum, thus she would not allow Alice and the remaining survivors to leave, even though the anti-virus remained in a suitcase on a platform outside of the room they were trapped in.
Alice refused to comply with the Red Queen and silenced the Queen's urging to murder Rain with the blow of an Axe to the security monitor she was speaking from. They would have remained locked in the room had Kaplan (thought dead) not fried the Queen's circuitry, which unlocked all doors in the facility.
Following the destruction of the Red Queen, the group makes their way to the train where Alice kills the reanimated Spence and retrieves the anti-virus, injecting it into Rain. In bad shape from her bites, Rain makes Alice promise that if she turns into an Undead, Alice will kill her as Rain doesn't want to be one. For a moment, it appears as if Rain has died and Alice reluctantly prepares to shoot her only to have Rain reveal herself as still alive.
At that moment, the Advanced Licker attacks the train, scratching Matt. As Alice pins the Licker's tongue, Matt turns to push the button to open the doors in the floor of the train, only to find that Rain has died and reanimated as an Undead. The reanimated Rain struggles with Matt who finally shoves her off of him. As Rain goes after Matt again, Matt shoots Rain through the head with her own gun, killing her once more. Rain's body falls on the button to open the doors, causing the Licker to drop to the tracks where it catches fire from friction and is killed. Following the deaths of Rain and the Licker, Alice crouches in front of Rain's body and stares at it, saddened.
Five years after her death, clones of Rain, alongside Carlos Olivera and One appeared in the underwater facility, Umbrella Prime. Rain's clones were used to in facility testing scenarios to map how the T-virus would spread in an controlled environment in order to sell the virus to the highest bidder. Two clones of Rain were used in the Umbrella Prime experimentation. One, "Bad Rain", worked as the security detail of the facility, working alongside Jill Valentine. The other was civilian in the Raccoon City simulation. Neither clones were aware of the original Rain's relationship with Alice or her life. "Bad Rain" was studious, straightforward and to the point. "Good Rain" was a self-professed activist who disliked guns and advocated gun control. While "Good Rain" helped Alice in escaping the facility, she was killed by an Uber Licker. "Bad Rain" later infected herself with the Las Plagas parasite and gained invulnerability and superhuman strength. She was eventually dropped through the ice near Umbrella Prime to be consumed by the Majini Undead emerging from the flooded facility.
In a deleted scene, another civilian Rain clone was bitten and infected by an Undead. However, the third Rain character was later removed from the film.
Rain was a tough, intimidating, and no-nonsense, black-ops soldier whom firmly believed in following protocol. She took great pleasure demonstrating her skills as the team's expert marksman to others and was confident in her shooting and fighting abilities.
Despite her cold attitude, Rain was shown to be loyal to J.D and her team, refusing to abandon them or the mission.
As noted above, Rain was no stranger to fighting on the front lines, and indeed, she actually seemed to prefer it as opposed to using more subtle methods. This would sometimes put her on the wrong foot with her team, particularly Kaplan, whom she viewed as being too inexperienced on the field and relying too heavily on his technology. He nonetheless earned her respect when he sacrificed himself to give the others time to escape.
Although often coming off as violent, bad tempered, and cocky almost to the point of arrogance, she was ultimately shown to have a selfless side to her as she was willing to let Alice and Matt kill her to prevent the T-Virus from escaping out into the world.
She was shocked and disgusted by the dangerous and irresponsible experiments of the Umbrella Corporation and the lengths that they would go to prevent anybody who would try to blow the whistle on said experiments.
She was deeply afraid of losing her humanity, refusing to allow herself to become one of the Undead and ordering Alice to shoot her in the head if she turned.
Skills and abilities
Rain's role as the group's most skilled marksman is shown several times throughout the film.
Appearance and wardrobe
Rain wears a black short sleeved T-shirt with a round neck. Over this she wears a heavy duty black jacket. She also wears black combat pants over big black boots. On her right wrist she has a huge black watch. At different times in the film she wears different things over this basic uniform. She wears a gas mask, a welding mask and numerous rigs with straps for weapons, including a knife at her right thigh and a torch.
One of these rigs, or perhaps her jacket, has an "S" logo on it. She also wears large padded gloves. Her communication gear is often around her neck rather than in her ear. Her dark hair is pulled into a ponytail, there are loose strands of hair around her face.