William Blim's History
Early life and imprisonment
Billy was conceived when his mother, a benevolent demon, was raped by his father, an evil human. At some point, he induced a man to publicly beat his wife to death in a convenience store, and was subsequently banished to a prison dimension guarded by Skip.
Release
Three days after his imprisonment, Lilah Morgan hired a psychic to force Cordelia Chase to endure intense visions that began to cause her physical damage based on what she saw. When Angel discovered Lilah's involvement, he was forced to break Billy out of prison to save Cordelia's life.
However, Lilah's manipulations quickly came back at her when Billy touched her business rival Gavin Park, who had tried to take credit for his release. This led to a confrontation in which Gavin beat Lilah, leaving her face heavily bruised.
Crusade in L.A.
Around that same time, Cordelia had a vision of the past convenience store attack. Angel Investigations got on the case; studying the security cameras, they discovered Billy's involvement.
Shortly afterwards, Billy willingly informed the police of his actions to get out of his family's estate, as they had been trying to keep him isolated. Angel tracked Billy down and confronted him just as the police arrived. However, as he was being escorted out of the house, Billy touched a male cop, resulting in a fight between him and his female partner, allowing Billy to escape from the car accident. Due to the smell of his blood, combined with the realization that he was able to enter the Blim estate uninvited, Angel noticed that Billy was not fully human.
Wesley, Fred, and Gunn took some blood samples from the crime scene to study, but in the process, Wesley and Gunn touched some of the blood and became infected themselves. This caused both men to act violently against Fred, but she managed to knock them unconscious and escape.
Billy proceeded to confront his cousin Dylan at a party, planning to head to Santa Monica and escape on a private plane. After interrogating Dylan and Lilah separately, Angel and Cordelia followed him to the airport. Cordelia arrived first and threatened him at crossbow-point; in an effort to save himself, Billy attempted to prevent himself from making genderist comments, but just couldn't keep from slipping and doing so, much to Cordelia's annoyance.
Death
At that moment, Angel arrived to take Billy on himself. Using this to his advantage, Billy touched Angel and goaded him to attack Cordelia. Instead, Angel turned and attacked Billy, revealing himself to be immune to the hatred. The fight, however, was cut short when Lilah arrived and shot Billy in the back, killing him.
In the aftermath, Angel explained to Cordelia why he was unaffected by Billy's touch: "I gave up on hate a long time ago"; even when he was soulless, he only killed for sport of pleasure and never felt any anger or hatred towards his victims. Cordelia remarked that, in a very strange sort of way, the demon inside of him was less "petty" than humans
