Pearl's History
Early history
Pearl and Nash were born in 1935 to Susan Finney, a human who had intentionally bred with a demon, believing her children to be the next step in evolution. In 1940, at the age of five, the twins were schooled regularly by their mother about their greater purpose and taught to live up to it the best way they could.
In 1953, Pearl and Nash sought in Rome partners to procreate with. Pearl had sex with a Black widower demon before it attempted to eat her. Spike suddenly appeared in the room and killed the demon, who was in debt with the vampire, inadvertently rescuing Pearl. She proclaimed Spike as her hero and became fascinated with him.
In 1970, Pearl and Nash both followed their mother's plan and bred with demons themselves. All of their children were killed by monster-hunters however, among then Alasdair Coames. Their mother suggested to them that, instead of breeding with demons, they breed with humans possessing strong magic, since not being able to blend in made their children vulnerable.
Twilight
Many years later, Pearl and Nash were approached by the masked Twilight, who told them of his plans to create a new, evolved universe, which along with his promise of bloodshed made them agree to work for him. Under his leadership, they killed Nadira's squad of Slayers in the Azores.
Angel eventually reneged on the Twilight affair, and Pearl and Nash vowed revenge against him. During the end of magic, their mother was no longer able to mystically prolong her life, and she asked her children to kill her.
After Pearl and Nash massacred the patrons of a bar in London, Whistler informed them that the world didn't know it was dead yet and needed to evolve. The twins accepted Whistler's proposition for the sake of bringing in the next stage of evolution and getting payback on their old boss, something their mother had supported.
Working for Whistler
Attempting to find Angel, the three half-demons tracked him to the Giles residence, where they only found Lavinia and Sophronia Fairweather, as Angel was currently in Quor'toth. Whistler informed Giles's great-aunts that he intended to complete the ascension that Buffy and Angel had interrupted as part of a plan to save the world by evolving it to the next stage, and he told the aunts when and where Angel should meet him.
Later, the three half-demons concluded a pact with a living Eyghon the Sleepwalker to try and restore magic using accumulated magical artifacts to trigger a magic plague, with Whistler agreeing to give Eyghon control of Europe after magic had been restored, to rule as he sees fit. However, Eyghon didn't trust Pearl and Nash, conscious and afraid that they didn't want to share the power and would try to double-cross him.
When Alasdair's cloaking device for his magical items was shut down in an effort to help resurrect Giles, Whistler and his group quickly went after them. Pearl and Nash fought with Angel and Faith then escaped with the items.
With Giles resurrected, Angel and the others headed out to stop Whistler's plan. In the ensuing confrontation on a rooftop in Hackney, Angel attempted to reason with Whistler, who still believed that he was saving the world and unleashed a magical plague, mutating the several people who had gathered to watch the fight.
Magic Town
Although their plan was successful, a revengeful Nadira killed Nash, and a remorseful Whistler absorbed the plague ball to prevent it from spreading globally, charring his body to a fatal level. Alone, Pearl escaped unseen.
Months later, Pearl became the muscle of the mutated pixie Corky Smallwood while remaining vengeful against Angel. Angel found her after he followed some teenagers filling bottles with pure magic back to Corky's hideout. Pearl attacked Angel and initially bested him, but he managed to blind Pearl with a bottle of magic. Corky reminded Pearl not to gloat, and she flew off into the night, warning Angel that this was not over.
