Willow Rosenberg (1981-?) is a powerful witch and a longtime friend and ally of Buffy Summers, the current vampire slayer. She uses her knowledge of magic to help fight the forces of evil.
Willow first met Buffy her sophomore year of high school. Initially, Willow was a shy and withdrawn student at Sunnydale High School. She excelled at school and was particularly knowledgable of computers and science.
Soon after Buffy arrived in Sunnydale, she saved Willow from a vampire. Following that incident, Willow, along with classmate and best friend Xander Harris, aided Buffy and her Watcher Rupert Giles in protecting Sunnydale from all kinds of supernatural threats.
Willow began experimenting with magic as early as age 17. She also dated Oz, a fellow classmate and werewolf.
Willow graduated from Sunnydale High School in 1999 and enrolled in The University of California Sunnydale where she roomed with Buffy. After a painful break-up with Oz, Willow joined an on-campus Wicca group. There, she met Tara and persued a romantic relationship with her.
Willow and Tara shared a generally smooth relationship whose only argument was over the growth of Willow's magic. When Tara's mind was drained by Glorificus, Willow saved her, and they patched things up.
Eventually, Tara felt that Willow was abusing her power and broke up with her. This caused Willow to even further succumb to the darker side of magic, but after a recovery, she and Tara got back together. Soon after, Tara was murdered by Warren. Willow absorbed dark magic, causing a change in her appearance, and eventually killed Warren.
Buffy and her friends tried to stop Willow from killing Warren's accomplices, Johnathan and Andrew, but they didn't have much success until Giles confronted her with borrowed power from a coven. Willow absorbed Giles' power and then tried to destroy the world. Xander was able to help her find her humanity.
Willow spent the summer of 2002 in England with Giles training in the use of her powers until she returned to Sunnydale in the fall. Willow was hesitant to use magic, especially after an encounter with The First, but she soon overcame her fear. She also began dating a potential slayer named Kennedy.
In the final battle with The First, Willow channelled her power through an ancient scythe and turned all the potential slayers into full vampire slayers. This process briefly turned her hair white, as opposed to the dark magic turning her hair black.
Following the end of Buffy, Willow is mentioned two more times. Andrew tells Spike, that she and Kennedy went to South America. Later, Angel, tries to contact her, and Giles tells him that Willow is on the astral plane.