26 years ago - Rachel Roth is born, the daughter of the high demon Trigon and a teenage runaway that had been given to him as an offering by a cult. Her mother flees into the alternate dimension Azerath, where she takes the name Arella and they are taught by the mystic Azar.
10 years ago - 16-year-old Rachel is taught about her father by her mother after the death of the mystic Azar. She takes the name Raven, swearing to stop her father. She travels to Earth & assembles a new team of Teen Titans, who succeed in trapping Trigon in an interdimentional prison.
8 years ago - 18-year-old Raven is overwhelmed by her father Trigon when he escapes his prison. Together they imprison the entire dimention of Azerath. She manages to manipulate the Teen Titans to kill her. This ends Trigon's hold on her & allows the imprisoned denizens of Azerath to weaken Trigon so that the Titans can kill him. Her mother Arella sacrifices herself so that Raven's soul can be reborn, and she appears to ascend to a higher plane.
3 years ago - 18-year-old Raven's soul is recalled from it's extraplanar existance to be imprisoned in a newly grown body grown by the Blood Cult, in order for her to become the consort of Brother Blood. she is saved by the new Teen Titans, and joins them.
2 years ago - 19-year-old Raven follows Gar Logan when he leaves the Titans to rejoin the Doom Patrol.
Raven has such an incredibly dark backstory that it's amazing she was part of a mainstream team like the Teen Titans, but it's a testament to the creative prowess of Marv Wolfman and George Perez that such a challenging concept could be featured so prominently on one of the best selling books of it's time. Their Titans team was clearly built around emotional archetypes, and Raven is built to represent the Yang to Starfire's Yin, but the entire concept of her character carried such dense narrative weight that the whole history of the Teen Titans was forever altered, and the team was elevated to the status it has reached today.
Obviously, there's no way to tell Raven's story without mentioning the animated series, where Raven quickly stood out as a fan favorite character. Much of her later stories are told with the very specific intent of recreating the character as she's depicted on that show. It was during this era that Raven was reborn by the Blood Cult with a younger body, now roughly the same age as the current generation of Titans. Also, it was during these comics that Raven's relationship with Beast Boy begins to develop in earnest.
Raven had appearances between the original Wolfman/Perez team and her later resurrection alongside Cyborg's next generation Titans, but we've used the defeat of Trigon as the catalyst for her apparent ascension to a higher plane in an effort to streamline her story. Also, we've deliberately made her relationship with Gar a larger crux in her life, moving her into the Doom Patrol, a team she seems uniquely suited for. Usually, making a character's story focus on his or her romantic relationship is an easy way to weaken their story. In Raven's case, however, her relationship is a key part of her ongoing quest to master herself and her emotions, and Gar's development into a heroic leader is strengthened by his desire to help people heal, and that is personified best by his closeness to Raven.