Raven is the daughter of a union between Trigon the Terrible, a powerful extra-dimensional being, and Arella, a woman who was part of a cult to try to bring Satan to earth. Instead, Trigon came and took Arella as his bride. Arella was rescued by an extra-dimensional pacifist cult and taken to the other-worldly dimensional world known as Azarath. There, she gave birth to Raven. The moment Raven was born, Trigon's evil influence was felt in Azarath. The grand-daughter if the original Azar herself raised Raven and trained her to keep her emotions in check, otherwise Trigon's evil side within her would be set free.
Raven's hair grows long in the future vision; Her hair actually resembles her comic book counterpart in that vision.
Trigon first appeared in Nevermore (2003) as a vision inside Raven's head. This is his official debut on the show.
Dr. Light's surrender to Raven is due to his frightening defeat at her hands in Nevermore (2003). Dr. Light also uses his souped-up super-suit, which was seen briefly in Wavelength (2004). This continues to reflect Dr. Light's bumbling persona from the comic book series. In this episode, he commits a crime the Titans see from their living room.