Name: Rain
Origin: Edenia
Race: Edenian
Playable Debut: Ultimate Mortal Kombat 3 (home)
Unplayable Debut: Ultimate Mortal Kombat 3 (arcade)
Story: Rain was the young son of a general in King Jerrod's royal armies (a popular name in fanfics are General Storm). When the invasion began, Rain's father fought valiantly for his homeworld. He and his contingent were captured, and, when the Dark Armies of Shao Kahn reached the palace, they were killed by Kahn himself in front of the royal family as a show that Kahn was quite serious about his demands: Sindel as his bride and Edenia as his world.
Sindel denied him. Kahn decided to eliminate the competition and killed Jerrod. He then transformed Edenia into the Outworld. He took Sindel as his unwilling bride and Kitana as his step-daughter.
When Rain was turning five, Sindel arranged to have him smuggled from the realm. Kahn, who wished to have the Edenian children trained as assassins for him, was furious. But he never discovered that Sindel was responsible for his disappearance, and let it lie.
The man who had smuggled Rain away took up dwellings on Earth, and trained Rain as a warrior. He told Rain the stories of the Outworld invasion, but never of the Edenian's true past.
Centuries passed, and finally, the Outworld invasion of Earth began.
In the invasion, Rain's tutor was slaughtered along with every living soul on the planet. Rain then traveled to Outworld, and presented himself as an assassin to Kahn. He knew that he was a Chosen Warrior of Edenia, but chose to betray his world rather than die at the hands of Motaro and his extermination squads.
Rain fought against Earth's forces until the resurface of Kitana. She told him of his true past. He was enraged and followed her to confront Kahn. Kitana was severely wounded in battle with the emperor, but she told Rain to take Kahn out for her.
Rain witnessed the apocalyptic destruction of Kahn. He then returned to Edenia, and took his father's former position at Queen Sindel's side.
Two years later, Shinnok snuck into Edenia, and his reign swept over the realm quite quickly. He then took his army of darkness, and waged celestial war on the Elder Gods themselves.