Lasciel

Lasciel, also known as the Seducer, the Webweaver, and the Temptress, is a Fallen Angel and a member of the Order of the Blackened Denarius. She first appears in Death Masks.

Description
She seems to be a black sheep among the other Fallen; "a rebel angel among rebel angels." As such, she isn't trusted by Nicodemus Archleone, and her coin isn't given to people lightly. Father Forthill comments that it was very odd that Archleone would want to free her (by giving her to Harry Dresden) since she does not follow Anduriel's lead.

In Small Favor, Archleone comments that Lasciel was the perfect coin for Dresden, suggesting that she was the only Fallen who had a chance to turn him. Her nickname of "The Temptress" and "The Seducer" appear to be well-earned, as Dresden constantly has to remind himself what she really is whenever she manages to connect with him or make him sympathize with her.

The sigil on her coin is "vaguely suggestive of an hourglass". The coin was supposed to be in secure storage in a Chilean monastery. Yet, it is in Archleone' possession to toss at little Harry Carpenter.

Death Masks
In Death Masks, Nicodemus Archleone tosses the coin in front of toddler Harry Carpenter just as Dresden was walking up to the child. Dresden's subconscious decides to pick up the coin in place of the child, and he buries it in his lab within his circle under concrete surrounded by a powerful binding spell.

Dead Beat
In Dead Beat, at Bock Ordered Books, Harry Dresden encounters "Shiela" who seems to have perfect recall and helps him find Die Lied der Erlking ; Bock seems nervous at the interaction. She later calls Dresden saying she is scared so he meets her at Bock's again; Bock appears frightened as they talk, and tells Dresden not to come by anymore. That night, after using Hellfire, Dresden has an odd dream with a hot tub set in a cave. Lasciel appears to him and explains that now that he has used some of the power she offers, she is able to interact more directly with him. She makes him an offer to aid him in fighting the Necromancers by teaching him secrets of his craft unknown to mortals. Dresden sees through her offer of Power and declines.

Later, Dresden meets Shiela at her apartment and has her recite the entire Erlking book for Dresden by memory at her apartment in an attempt to discover the summoning ritual. Afterward, they kiss. As he prepared for his battle against the Heirs of Kemmler Dresden returned to Shiela's place with Waldo Butters to check on her. When Butters comes in, he asks Dresden who he is talking to; realizing what was happening, Dresden used his Sight and discovered that Shiela was an illusion that Lasciel created so that she could help Dresden, fearing that the death of Dresden would mean the death of part of her. She claimed that she intended to tell the truth to him afterwards, but she didn't want him distracted.

Proven Guilty
In Proven Guilty, Lasciel is still attempting to persuade Harry Dresden to take up the coin. She offers him assistance in his investigations, but Dresden won't allow her to influence him. She also points out the similarities between Nelson Lenhardt, Molly Carpenter's boyfriend, and Dresden.

White Night
In White Night, Harry Dresden has taken to calling it "Lash". Lash is a separate character from the "real" Lasciel at this point in the series.

Dresden talks about temptation and choice with Lash. He suggests that maybe being inside of him has had some effect on her, just as she has had some effect on him. When Lash is taken back into the whole, she will be gone: die. He then plants the seed that Lash has free will, too and that she can choose for herself, have a life outside of Lasciel.

In the battle of the Deeps, during Vittorio Malvora's crippling attack of despair, when Dresden and his friends about to be overrun by ghouls, and a bomb is about to go off, Lash speeds up his mind to effectively slow down time. She makes a bid for him to call the coin to him—he refuses, and asks her to help him instead. Lash initially refuses, pleading with Dresden that Lasciel would never forgive her, never take her back, if she failed here. Realizing that Dresden would rather die than summon Lasciel, Lash concedes that she has a choice and finally separates fully from Lasciel, saying that "I-she doesn't deserve you." Then, she tells him that Vittorio Malvora is possessed by an Outsider. Due to the circumstances of his birth, he has the potential to wield power over Outsiders. Dresden can shake off the spell and she will give him the opportunity to do so. Then, she walks away toward Vittorio.

Lasciel's coin was given to Father Forthill, who placed it with the rest of the coins the Knights of the Cross had collected. At some unspecified point afterwards the Coin vanishes.

Small Favor
In Small Favor, Michael Carpenter is suspicious of Harry Dresden because of Lasciel. When Dresden confronts him, Carpenter points out that nobody has ever gotten rid of the shadow of the Fallen without summoning the coin, and notes that he has never told him how it happened. Dresden just tells him that it wasn't fair what happened to Lash.

After the attack on Demonreach, Nicodemus Archleone attacks Dresden, and comments on his surprise that Dresden hasn't taken up the coin in spite of the years Lash had to reason with him. He then orders the shadow to incapacitate him, not knowing that it was gone.

Skin Game
In Skin Game, Lasciel takes advantage of Nicodemus Archleone's betrayal of Harry Dresden in Hades' Vault to take Hannah Ascher as her host. She is motivated to kill Dresden by both her desire to save her child and her pride by his refusing her, since she had never been rejected before. She guides Ascher in a fight with Dresden, which Dresden wins. After Ascher's death, Lasciel's coin remains in Hades' Vault.

A spirit of intellect resulting from Lash's death is growing in Harry Dresden's brain, with all the knowledge and power of both Dresden and the Fallen Angel but without any idea of what to do with it; without proper guidance, the spirit could be very dangerous.