Cordelia Chase was born into a rich family. They lived in the town of Sunnydale, California. She is very popular and beautiful and very selfish. Her best friend was Harmony Kendell. In her sophomore year she became friends with Buffy Summers, the new girl who transferred form Los Angeles. Buffy on the other hand couldn't stand her snobby, bullying, behavior to other people. So she deiced to "leave" Cordelia and became friends with Willow, Xander, and the school Librarian Rupert Giles. Because Buffy "left" her she decided to make Buffy's life a living hell, to make her an outcast as much as possible. Even though Buffy saved her life on more than one occasion.
Cordelia began dating Xander Harris. They started their relationship when they were hiding in Buffy's basement from a demon who could turn into maggots. Though they dated each other they decided to keep it a secret. When her friends (the cordettes) found out about their relationship she couldn't hold out against the pressure and ended their relationship. Xander later used witchcraft (through Amy) to make her fall in love with him but instead it made every other girl in Sunnydale fall in love with him. Even to the point of almost beating Cordelia to death for dumping him. She later witnessed Xander and Willow kissing. While doing so she fell through the floor and was impaled with a bar. While in the hospital she broke up with Xander.
Angel and Angel Investigations
Though she was accepted to colleges like Columbia University, she was unable to afford them. She moves to Los Angeles to become an actress. Meeting Angel (whom she had met while still in Sunnydale) She tells him that she is a rich and successful actress. When she is in fact almost penniless. After being rescued by Angel from a vampire attack she "charms" Angel into letting her become his partner in battling the forces of evil. She becomes a partner in Angel Investigation's Office manger. Though the season of the show she begins to have a love/annoy relationship with Doyle (who was part demon which she never knew until his death).
When Doyle died he passed the "visions" on to her with a kiss. The visions are messages from the powers that be.
As the only link to the powers that be. Cordelia consider the visions the only reason for being. Because only demons are strong enough the visions were slowly killing her. Causing her brain damage. For months she begins to take powerful painkillers. Angel later found her CAT scan that showed her deteriorating brain tissues.
As the visions are powerful enough to kill a normal person they are only meant for "good" demons to use. Cordelia finds this out on her 21st birthday when a powerful vision sends her to the astral plane. There she met a demon guide Skip. He later transforms her into a part demon. Now part demon she no longer has intense pain when having the visions. Though there are side-effects, she finds them as part of her demon powers, and not a bad thing. Unbeknownst to her team, the change makes it possible for her body to be used by the forces of evil. Her former guide Skip turns out to be an agent of evil. He makes Cordelia believe that she can do more work/good in a higher plane.
Goddess Cordelia/ return to the lower plane
For the three months that she is on the higher plane she is unable to communicate with anyone on Earth and as an effect she is bored. She finally returns but she has lost all memories. Now lost and confused she takes refuge with Angel's son Connor. During her time with him she feels lost and confused about not remembering her past. Connor offers to train her just as Angel did. Because she was a former cheerleader her athleticism and her "warriors heart" makes her a better than average fighter.
Her memories are finally brought back to her with a spell from Lorn. The spell also awakens the fallen power that hid inside her. The godly being known as Jasmine intertwined itself with every fiber of her being. Jasmine now in sub-conscious/conscious control makes Cordelia and Connor more close to each other to the point where they have sex. This gave Jasmine the "seed" she needed to escape and be born. A few months later (definitely not a full 9 months) Cordelia/Jasmine gave "birth" to itself, and Cordelia 's body was left in a deep mystical coma, having been drained of all her energy.
After several months in the hospital Cordelia awoke from her coma. She was shocked to learn that Angel and the team were now in charge of Wolfram & Heart (just the L.A. branch). Angel told her that using the infinite resources of the company that they could do more good in a day than they would do in a year at the hotel. She doesn't agree she calls it a "deal with the devil". She later learns the the real reason that Angel became a part of Wolfram & heart was to have them erase his son's memories and have him lead a peaceful life with a normal family. Learning this she forgives him. She later tells Wesley that she is sorry for killing Lilah while under the control of Jasmine. He assures her that he doesn't hold her responsible. Later, Cordelia tells Angel that she cant stay because this isn't her world anymore. She reveals to Angel that the Powers That Be owed her a favor and she used it to get "her guy back on track". They kiss one final time as the phone rings and she tells him he has to answer it. It is the hospital calling to tell Angel that Cordelia died in her coma, when he turns to tell them that she standing right there, she is gone. He realizes that she never really woke up to the rest of the world and she's gone.
Deceased but... Ascended
In the canonical comic book continuation of the television series Cordelia appears in the twelfth issue (Her presence also is hinted in the ninth issue) as a guide to Angel in his dying moments; it's revealed she serves as a higher power now. Cordelia also appears in a dream sequence within the twentieth issue of Buffy's canonical continuation.
Powers and Skills
She was originally just a normal human, After having the visions passed to her by Doyle she began having incredible visions of those in need of a champion. These visions were incredibly painful as well and almost killed her. This changed when she was transformed into a part-demon with the ability to resist the harmful effects of the visions, levitate, and the radiate a bright golden, white light to purify evil (like otherworldly slugs or Connor's tainted soul). She grew to have some control over this ability which she could use it as a nightlight. When she was possessed by Jasmine she controlled The Beast, used magic, communicate telepathically (with the use of an enchanted stone), manipulate Lorne's empathic powers, and (for a very short time) she was able to hold her own with the most powerful witch in the Buffy/ Angel universe Willow.