Darla was born in the late 16th century in the Virginian Colonies. Her birth name has never been revealed and she herself eventually forgot it. As a young prostitute, she became independently wealthy but also contracted a fatal case of syphilis. By 1609, Darla lay dying in the luxurious house she owned in the British Virginia Colony in North America. She scoffed at a "priest" who came to her deathbed, before he revealed his true identity: the Master, leader of the elite cult of vampires known as the Order of Aurelius. Darla despised the clergy and religion – a trait that would follow her as a vampire. The Master turned her into a vampire and named her "Darla," meaning "dear one" in early modern English ("darling").

As a vampire, Darla enjoyed luring hapless males by appearing as a seductive and mysterious yet innocuous woman. Many examples would prove Darla as a predator who preferred using her good looks instead of hunting to obtain victims. She's not as sadistic as Angelus or violent as Spike.

By 1753, Darla was out exploring the world and wreaking havoc when fate brought her to a small town in Galway, Ireland. There she found a man named Liam, who was drinking and whoring his way through a rather uneventful life. Admiring him from afar, Darla lured Liam into an alley where she sired him, and Liam became Angelus. Waiting for him atop his grave, she gave him his first lessons on being a vampire after he slaughtered his entire village and killed his family, telling him that his acts were a way to react to his father's disapproval.

After cutting a bloody swath across Wales and England, Darla brought her new consort back to The Master in London, but Angelus had no interest in The Master, the Order of Aurelius, or anything other than living a decadent life of pleasure and sadism with Darla by his side. Darla chose Angelus over her sire. Over time, Darla and Angelus would make their way throughout Europe and North Africa, occasionally sparring with each other but constantly tormenting the vampire hunter Daniel Holtz.

Back in London, Darla and Angelus' "family" grew when Darla lured Angelus to Drusilla in 1860; the addition of Spike in 1880 would complete the vampire foursome. Throughout their adventures, Darla always demanded a room with a pretty view. It was during this time that Spike first heard about Slayers from Angelus while Darla and Drusilla watched them spar.

Finding themselves in Borsa, Romania, in 1898, Darla brought Angelus a gift: a Roma girl with whom Angelus could have his way, so long as Darla watched. Soon after, the family of the girl, the Kalderash Clan, cursed Angelus with the restoration of his soul. Darla sensed the restored soul in her beloved, and banished Angelus from her sight. Obviously bewildered, she tracked down the Kalderash Tribe alongside Spike and Drusilla, and massacred the village, though she met with the girl's father, one of the Kalderash Elders, and offered to spare his other daughters in exchange for the removal of Angelus' soul. However, Spike had already killed the daughters of the elder.

By 1900, Darla took Spike and Drusilla to China, never telling them about what had happened with Angelus. The trio ended up in the midst of the Boxer Rebellion, and there Angelus found her. Angelus tried to convince Darla that she could still be with him despite his soul, but she soon realized that it could never work, as Angelus could not bring himself to injure innocents.

Darla's story through the Boxer Rebellion unfolds in flashbacks scattered among numerous episodes of both Buffy the Vampire Slayer and Angel; they were not presented in chronological order. A guide to finding the flashback or flashbacks to a particular event is at "List of Buffyverse historical flashbacks".

Sunnydale

Little is known about Darla's activities between the Boxer Rebellion and 1997, but at some point she rejoined the Master and the Order of Aurelius, and comes to Sunnydale, California. When Buffy Summers ends up in the same town, Darla meets her in a mausoleum entrance to the dungeon. The Master is not pleased. After several attempts to have the Slayer killed fail, Darla finally volunteers to kill her herself. Darla pretends to be a school friend of Buffy's and gets Buffy's mother, Joyce, to invite her into the house. Darla bites Joyce but cleverly sets it up so that it appears that Angel is the culprit. After a tense three-way confrontation in The Bronze, Angel finally stakes Darla, turning her into dust, but that is not the end for Darla.

Los Angeles

Nearly three years later, Darla is resurrected, in human form, by Wolfram & Hart as a way to both torture Angel and reawaken Angelus. During her short time as a human, Darla finds it increasingly difficult to live with a soul and desperately wants to be a vampire again. Angel, through acts of bravery and nobility, finally convinces Darla to live out her remaining days as human (she is dying from syphilis as she would have if she weren't sired the first time) and reassures her that he will help. In a cruel twist of fate, Wolfram & Hart bring in Drusilla to sire Darla (Charles Gunn comments that the concept of the granddaughter remaking the grandmother freaks him out more than the vampire thing).

A vampire once more, Darla goes on another killing rampage with Drusilla that nearly ends when Angel, having begun a rapid descent into darkness that puts him somewhere between Angel and Angelus, sets her and Drusilla on fire; fortunately for the both of them, Darla and Drusilla survive. Angel's life perspective grows darker when he is told that nothing he does apparently matters, and he comes to Darla to help him "not care." Angel and Darla have sex, the expectation on Darla's part being that he will have lost his soul as a result of "a moment of perfect happiness" (the other half of the gypsy curse), but the next morning, Angel is still ensouled; sex with Darla was only perfect despair, rather than perfect happiness. Surprised, angry, and upset, Darla leaves Los Angeles, supposedly forever.

However, the unthinkable has happened: Angel has impregnated Darla. Darla visits every shaman in the Western Hemisphere, who all tell her one thing: her pregnancy is inherently impossible, and yet also impossible to abort. With nowhere else to turn, Darla goes to Angel. Various theories emerge about the child; from a cult of vampires worshipping it as a miracle, to the fear that it is the evil spoken of in the Tro-Clon prophesies. It turns out the child is simply a healthy human baby boy, with whom Darla is sharing a soul. This does not matter to Daniel Holtz, who had been brought through time by the demon Sahjhan to hunt and kill Angel and Darla.

Darla realizes that she will lose her soul after giving birth, and will no longer be able to love her child. Additionally, her undead body is becoming increasingly unable to sustain the life of her unborn child in time for it to be born. After telling Angel to make sure that their son knows that he was the one good thing the two vampires ever did together, Darla stakes herself in the alley behind Caritas, leaving behind a pile of dust, and a crying, but healthy, infant. In one final moment of redemption, Darla ends her 400+ year run in exchange for the life of her son, whom Angel names Connor.

Sometime later, Darla's spirit appears to a now-teenaged Connor when he is being tempted by the now-villainous Cordelia Chase to murder an innocent teenage girl. Claiming to have been sent by the Powers That Be, Darla pleads with her son not to commit murder. Seemingly moved by his mother's words, Connor begins to untie the girl, but Cordelia chastises him for allowing himself to be swayed by Darla's spirit, whose presence she can sense, and she kills the girl instead. Darla disappears, and Connor never mentions their conversation to anyone.