Darlas life began long before we meet her in the Buffverse, born under a different name her life was one of desolation and misery until she began to user her body for money. Becoming a prostitute after she immigrated to Virginia in 1609 she was a talented and popular prostitute soon becoming immensely wealthy. Struck down with a severe case of syphilis in 1609 she lay in her death bed ever the sight of misery and acceptance, she was still fighting as a priest visited her. Darla scoffing screamed for the priest to leave until he revealed himself to be The Master the leader of a band of ancient vampires who labeled themselves the Order of Aurelius.
Darla was born into the vampire world and took to it with passion and grace, soon becoming the Masters favorite. He named her Darla after the Gaelic term meaning Dear One. Darla became a collector of beautiful men and by the 17th century was one of the most feared vampires. Circling the globe with the Master she worked for his cause while hunting her favored prey. Angelus having no love of the Order pulled Darla away from the Master and into his arms.
It was in 1753 that Darla found a handsome and useless young Irishman named Liam, flaunting his wealth through drink and women Darla lured him to an alleyway and turned him. Liam would soon be named Angelus the most evil and violent vampire ever created. Darla had finally found the one she was looking for, a partner who shared in her love of death and mayhem, Angelus and Darla swathed across the British isles they began to torture a man named Holtz. A man who hunted vampires for a living. Taunting the man the two of them killed and mutilated his family Angelus raping and torturing his wife while Darla sired his youngest daughter and killed his infant son. Leaving a note behind that simply said "how can you save others when you can not even save your own".
Holtz in his mayhem hunted the two with renewed vigor, finally trapping them in a barn in France, setting fire to the barn to hunt them out, Darla abandoning Angelus for safety was tracked down by him later and the pair reunited, later Angelus would betray Darla by letting the hunter know her whereabouts.
Chased through out the world by Holtz Angelus was finally captured by Holtz and a catholic group, tortured by the group Angeuls laughed through every minute, infuriating Holtz until Darla rescued her lover and took them away from Holtz, letting him know they would pay him back for it all one day.
Back in the world the pair would now collect the new members of their family, Drusilla and then William (spike) would join them both and help to hunt humans across the globe. A happy family they would all share the love and welcome each other into their murderous rampages.
It all shattered for Darla in 1894 Angelus after torturing a Romanian gyspy princess was punished by the tribe, his soul was placed back in his body. Darla at first left Angelus to his own disgusting soul but soon came back to try to beg the King of the tribe to take his soul away, however after Spike and Drusilla destroyed the village he refused, Drusilla taking his life with a snap of the neck.
Abandoning Angel she took of with Spike and Drusilla but soon ditched the lovers to return to her beloved Master. His new mission to take over the world and destroy the slayer would take them to Sunnydale
Following him to Sunnydale she was once again faced with Angel, disgusted at his love for Buffy she attempted to kill him and the girl. Put down by Buffy she fled, attacking Buffys mother and dropping her in Angels arms to try to destroy the lovers, but it turned against her when Angel staked her.
Resurrected by Wolfram and Hart to help deal with Angel, Darla was once again human and possessing a soul. She taunted Angel in an attempt to break his spirit and trick him into siring her because she was unable to cope with all the evil that she did as a soulless vampire. Unbeknownst to Angel and even to Darla for a short period of time, Darla was resurrected exactly as she was as a human: suffering from a fatal syphilitic heart condition.
Angel tried to help Darla through the transition to possessing a soul, but when they discovered her fatal condition he began to look for ways to cure her. Angel fought through several trials to earn a second chance at life for Darla; however, once he succeeded the gauntlet, it was proven futile because this was Darla's second chance. [Unknown to everyone, these trials allowed for the creation of Angel and Darla's son]
Since Angel refused to sire Darla, Wolfram and Hart summoned Drusilla to forcefully turn Darla into a vampire (with Darla effectively becoming her vampire grandmother and daughter). Reunited with Drusilla and the pair would cut a rug throughout the town before Angel and the crew would find and nearly kill them. Setting the pair on fire he walked away as they burnt, but Drusilla managed to save them with a fire hydrant.
Angel during a dark period went to Darla to talk about his past and ended up having sex with her, disgusted with his actions he abandoned her soon after.
Not long after Darla would appear on his doorstep heavily pregnant, the first documented Vampire pregnancy. Angel hunted down every Shaman in town to try to discover if the child was a demon or human and none could say.
Protecting her from Wolfram and Hart Angel and Darla were finally able to reconnect over their past and heal from it As Darlas body began to die the pregnancy eating away at her flesh, she realized that her life was nothing until this point and that the child they created would be her redemption.
Her final act on earth killing herself to save the life of her child Connor.
Later Darla would appear as an angel to her son to help guide him back on his right path.
"This child, Angel... it's the one good thing we've ever done together. The only good thing. You make sure to tell him that."