Lorne was born as Krevlornswath of the Deathwok Clan in the demonic dimension of Pylea. Lorne, as he prefers to be called, wasn't like his fellow Deathwok clan demons, bloodthirsty "champions" constantly undertaking quests against evil. He is a gentle soul who does not share his kin's prejudice against humans (or "cows" as they are called in his world). Lorne would rather flirt with the female demons and enjoy life than train to be a fighter. He also enjoys beauty, art, and even music, which was difficult, considering his world had no music. Lorne refused to train his innate mystical senses to learn to hunt beasts and is considered the shame of his clan.
In 1996, Lorne happened upon a dimensional portal and was sucked through it. He landed in Los Angeles and discovered music and culture like he never imagined. Lorne learned to hone his mystical senses to read people's auras, but found it easiest to do so when they sang, baring their souls. He opened up a karaoke bar on the same spot that he arrived on Earth, an old abandoned building. Lorne contracted the Transuding Furies to cast a sanctuary spell on the spot, which stopped any demon violence from occurring on it. He named the bar "Caritas," the Latin word for "mercy."
Caritas became a success in the morally ambiguous Los Angeles underground scene. To most who visited the bar, Lorne was simply called "The Host." He later states that he didn't use the name "Lorne" in this dimension, because his striking green skin prompted people to make Lorne Greene jokes.
Lorne is always reluctant to help Angel and the other heroes of the series, preferring to maintain a neutral stance and simply provide a peaceful place for all demons, but his essential goodness usually wins out over his reticence. He starts off by giving the characters advice and encouragement, but as time goes on, he becomes more directly involved in the cases of Angel Investigations- even asking for Angel's help to avert the end of the world when Angel had severed ties with the rest of the group after Darla's resurrection- and his many contacts in Los Angeles' magical underworld prove useful. Lorne somewhat reluctantly joins the team in their mission to Pylea to rescue Cordelia, discovering that he could incapacitate the natives by singing songs and causing them to cower from "the strange noise." On leaving, he decides that returning to Pylea had been good for him as it had reaffirmed that he did not belong there and was right to stay away.
In Season Three of Angel, Caritas is raided by Charles Gunn's old gang and it is temporarily put out of action, finally being completely destroyed by Daniel Holtz. After that, Lorne finds himself becoming far more attached to the AI team, and he often looks after the infant Connor while Angel is on business. Eventually, he leaves to start a singing career in Las Vegas, Nevada, but leaves after a crime lord forces him to use his empathic abilities to locate audience members with promising futures so he can steal them. Back in L.A. after being rescued by Angel, Gunn and Fred, Lorne helps restore Cordelia's lost memories and is part of the fight against the resulting Jasmine crisis.
In the show's fifth and final season, Lorne finds himself the new head of Wolfram & Hart's Entertainment Division, at first fitting into the job with relative ease and making various business deals in the film industry. As time goes on, his kindness is slowly replaced by a growing cynicism and self-loathing of his position of "cheerleader" for Angel and his friends, particularly when Gunn is abandoned in a Hell dimension to recover Lindsey McDonald because Lindsey could possess information they needed; Lorne had always assumed that they didn't leave anyone behind.
When his close friend Fred is murdered and her body usurped by the Old One known as Illyria, Lorne becomes filled with despair which he keeps secret from the rest of his equally heartbroken friends. By the conclusion of the series, he announces that he is leaving Los Angeles after carrying out his part in Angel's plan to destroy the Circle of the Black Thorn. When Lorne learns what his part is to be, he tells Angel "I'll do this last thing for you, for us... but then I'm out, and you won't find me in the alley afterwards. Hell, you won't find me at all. Do me a favor. Don't try." Lorne's part is to betray and murder longtime enemy-turned-ally Lindsey, who in his final words mutters at the unfairness of being killed by Lorne, a 'flunky', and not his longtime rival Angel.
In his final scene, after shooting Lindsey with a silenced pistol, a disgusted and broken Lorne walks off into the darkness. He drops the gun and simply says "Goodnight, folks" as he leaves.
In Angel: After the Fall, he is the Lord of Silver Lake. He tries to make his territory a Heaven in Hell, and holds a neutral status in Angel's war with the other Demon Lords. In Angel's battle with the Demon Lords' champions, Lorne rallies Angel's other allies to even the odds, thus fully reforming the Angel Investigations team.
In the episode "Life of the Party," Lorne's lack of sleep causes his subconscious to use his powers differently. Instead of reading destinies, he starts to write them, granting him a sort of mind control/suggestion power. He inadvertently transforms Spike into a super-positive person, makes Wesley and Fred act drunk despite Fred having had nothing and Wesley having barely had half a beer, Gunn urinate all over the Wolfram & Hart building (he had told Gunn to "stake out his territory," and Gunn responded by marking his territory in a manner similar to animals), and influences Angel to have sex with Eve after commenting on the sexual tension between the two. His subconscious, unable to cope with the conflicts Lorne usually handled in his sleep, then manifests as an astral projection which possessed superhuman strength and durability (it easily overpowered Angel and took multiple punches to the gut from him without even flinching), resembling a Hulked-out version of Lorne that attacked those who had angered Lorne recently, such as a demon who arrived at the party wearing human skin as a mask. These powers were lost when Lorne's ability to sleep returns to him.