Lasciel

Lasciel is a fallen angel and a member of the Order of the Blackened Denarius. Lasciel is also known as the Seducer, the Webweaver, and the Temptress. 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 and her coin isn't given to people lightly. 

Father Forthill describes her as "The Seducer", and she's also called the Webweaver and the Temptress. It seems odd to Forthill that Nicodemus would want to free her (by giving her to Harry) since she does not follow Anduriel's lead.

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 was in Nicodemus' possession to toss at little Harry Carpenter.

In the series

Death Masks

Main article: Death Masks

At the end of Death Masks, Nicodemus tossed the coin in front of toddler Harry Carpenter just as Harry Dresden was walking up to the baby. Harry's subconscious decided to  pick up the coin instead of picking up Harry himself. Harry buried it in his lab within his circle under concrete. 

Blood Rites, Dead Beat, Proven Guilty, and White Night

Main article: Blood Rites

Main article: Dead Beat

Main article: Proven Guilty

Main article: White Night

Afterward, in books Blood Rites, Dead Beat, Proven Guilty, and White Night, a copy of Lasciel took up residence in the unused portions of Harry's brain, with the intent of tempting him into taking up the coin permanently and becoming a member of the Denarians. Harry could converse with it. 

Dead Beat

Main article: Dead Beat

In Dead Beat, at Bock Ordered Books, Harry encountered "Shiela" who seems to have perfect recall and helps Harry find Die Lied der Erlking. She called Harry saying she's scared so he met her at Bock's. That night, after he used Hellfire Harry had an odd dream with a hot tub set in a cave. Lasciel appeared to him to make him an offer to aid him in fighting the Necromancers by teaching him secrets of his craft unknown to mortals. Harry saw through her offer of Power and declined.

Later, as Shiela, she recites the entire Erlking book for Harry by memory at her apartment. Afterward, they kiss. Harry returned to Shiela's place to check on her concerned for her safety. He discovered that Shiela was an illusion that Lasciel created for Harry wanting to help him against the Heirs of Kemmler fearing that the death of Harry would mean the death of part of her.  

White Night

Main article: White Night

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

Harry 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 Harry and his friends about to be overrun by ghouls, and a bomb is about to go off, Lasciel speeds up his mind to effectively slow down time. She makes a bid for Harry to call the coin to him—he refuses, and asks her to help him instead. Lasciel initially refuses, pleading with Harry that Lasciel would never forgive her, never take her back, if she failed here. Realizing that Harry 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 Harry that Vittorio Malvora is possessed by an Outsider. Due to the circumstances of Harry's birth, he has the potential to wield power over Outsiders. Harry can shake off the spell and she will give him the opportunity to do so. The she walks away toward Vittorio.

Lasciel's coin was given to Father Forthill in White Night, 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

Main article: Small Favor

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

After the attack on Demonreach, Nicodemus attacks Harry, 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

Main article: Skin Game

In Skin Game, it is revealed that Lash's death resulted in a spirit of intellect growing in Harry'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.

After Nicodemus betrays Dresden in Hades' Vault, it is revealed that Lasciel was back and using 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; according to her she had never been rejected before. She also claims to be the shadow who whispered in Dresden's ear the words that caused the events in Ghost Story. She guides Hannah in a battle with Dresden, who pleads with Hannah to break away from Lasciel, but Hannah ignores him and attacks with a blast of fire. Dresden blocks the blast and sends it into the ceiling, then falls on his knee with a shield in front of him; Hannah thinks he's finished, but Lasciel's eyes widen as she realizes what he had really done. A second later, flaming debris from where the attack hit the ceiling drop directly onto Hannah, killing her.

After Hannah's death, her coin is stuck in Hades' vault.