The Infernal Devices is a series of novels by author Cassandra Clare, centering on a race called the Shadowhunters introduced in her The Mortal Instruments series. The series is a prequel series to the Mortal Instruments series, and contains some of the character's ancestors. Clare has insisted that the series' can be read in any order.
The series follows Tessa Gray, an orphaned teenage girl who discovers she has the power to shapeshift, but doesn't bear a mark that shows she is a warlock, and abilities that plunge her into a world she never knew existed. She will have to learn to master them if she wants to find her brother Nate and she will have to forge an alliance with Shadowhunters if she wants to survive in this dangerous world.
The trilogy features Will Herondale, Jem Carstairs, Tessa Gray, and other Downworlders and Shadowhunters in the London Institute.
The series takes place in Victorian England, a short time after the peace treaties between Downworlders and Shadowhunters. As Shadowhunters consider themselves superior or purer than Downworlders or demons, they may have no qualms about killing either.
The first book in The Infernal Devices is entitled Clockwork Angel and begins the story of Tessa Gray, an orphan teenage girl who is looking for her brother Nathaniel Gray, who has disappeared, and seeks her true identity.
Her search plunges her into a world she never knew existed, and reveals talents she never knew she had. She will have to learn to master them if she wants to find her brother, and must forge an alliance with Shadowhunters if she wants to survive in this dangerous world. Many of the family names of the Shadowhunters used in The Mortal Instruments are first introduced in this series. Another character in The Infernal Devices, Magnus Bane, the High Warlock of Brooklyn, also plays a part in this series.
As Tessa Gray is drawn deeper into the Shadow world, and goes on the quest of finding her brother, she falls in love with two Shadowhunters–but when it comes to choosing one, trouble begins to brew and suspense finds its way into her life. She will have to learn to hide her feelings if she hopes to survive. However, as her heart rages for love but her mind is bent on saving her brother, will she hide her vulnerable side? Which of the shadowhunters will win her heart?
Theresa "Tessa" Gray: A 16-year old girl who has lived most of her life in New York until her brother Nate sends her a ticket to come to England. Upon arrival however, Tessa is taken captive by the women who introduce her own abilities to her, inevitably pulling her into the Shadow World. Later on in the series, herself and everyone around her (even the Silent Brothers) haven't the slightest hint in what she derives from—all that is known is that she has the ability to shapeshift into any person and acquire their memories, manners, and abilities after forming a psychic bond with an object of their possessions. She has grey eyes and brown hair. She is in love with and also torn between Will Herondale and James Carstairs.
William "Will" Owen Herondale: A 17 year-old Shadowhunter who chose to become a part of the Shadow World at the mere age of 12. He was born in Wales, can fluently speak both Welsh and English (along with Greek, Latin and many more languages), leaving a trace of an accent whenever he speaks. He is half-Welsh (from his mother Linette Herondale née Owens), half-Shadowhunter (Edmund Herondale). His parabatai is James Carstairs. He is known to have dark blue eyes, and black hair. He has a dry sense of humour and phobia of ducks, a trait that the Herondales seem to possess. He falls in love with Tessa Gray and cannot ever stop loving her. Will and Tessa do, in fact, end up together. It is known that they have 2 children, Lucie and James, after the series comes to an end.
James "Jem" Carstairs or Ke Jian Ming: A 17 year-old Shadowhunter, whom was forced to live in the London Institute after the slaughter of his parents from the Shanghai Institute. After being physically tortured by a demon, who constantly fed him with the drug yin fen and made his body addicted to it. Though the drug is slowly killing him, he is forced to live on it to stay alive. Being half-Chinese (from mother Ke Wen Yu) and half-English (from father Jonah Carstairs), he speaks fluent Mandarin. His allegiance is with the Enclave. His "parabatai" is Will Herondale. He is known to have silver eyes and silver hair: a side-effect from consuming yin fen, however, in the series "The Mortal Instruments" Jem makes an appearance, and his cured self is told to have dark brown hair and eyes. Jem falls in love and gets engaged to Tessa Gray throughout the trilogy, however, the engagement does not live through "Clockwork Princess" for Jem is turned into a silent brother in order to stay alive.
Sophia "Sophie" Collins: Prior working at the London Institute, Sophie was a parlor maid, working for the Atkins family in St. James Wood. She was very beautiful, therefor she was offered the job. Her employers son attempted to seduce Ms. Collins, but she turned him away repeatedly. The son raged out at her, and took and knife and cut open her face; Saying if he couldn't have her, then no one will ever want her again. Sophie went to her mistress but the boy claimed she tried to seduce him, and cut her to protect his virtue. She was thrown on the streets, and Charlotte Branwell then took in Sophia. Sophia was born with 'the Sight' therefore she could see Charlotte when she was glamoured at the time. Sophie is known to end up with Gideon Lightwood. They have 3 children (Barbara, Eugenia, and Thomas) after the trilogy is over.
Jessamine "Jessie" Lovelace: Jessamine is a Shadowhunter who detests everything about being a Shadowhunter. Despite loathing the Shadowhunter life and would do anything to leave it behind, Jessamine can be dangerous if she wants to be. She lost her parents when she was a child. She is also known to have a dollhouse in her bedroom of the London Institute, with "Baby Jessie" as Jessamine's calls the doll.
Henry Jocelyn Branwell: Absent-minded and brilliant, Henry spends his waking hours in the crypt of the Institute, inventing fabulous machines and weapons out of cogs, cams and gears. Unfortunately just as many of Henry's inventions don't work as the ones that do, and Henry is as likely to set himself on fire as he is to invent something new and amazing. He invented the portal with the help of one magnificent warlock, Magnus Bane.
Charlotte Branwell: Twenty-three-year-old Charlotte, wife of Henry Branwell, runs the entire Institute with a capable hand. Kind and loving, she does her best to care for the orphaned Shadowhunters who live under her roof whilst hiding her loneliness from the absent-minded husband she loves. It seems as if there's nothing Charlotte can't manage — until Tessa's search for her missing brother begins to uncover a web of corruption and deceit in London's Downworld that threatens to tear London's Enclave of Shadowhunters apart.
Axel Mortmain: The antagonist of this series and he is the one responsible for the clockwork creatures. He plots to destroy all Shadowhunters to avenge his warlock parents. He is a very dangerous man, and he needs Tessa Gray for the last key to his michevious plan to overrule the Shadowhunters. He is later known to have "created" Tessa.
Magnus Bane: An ancient warlock whose origins reside in Indonesia. He is flamboyant, but also wise. Early on, he has a romantic relationship with a vampire, Camille Belcourt. Magnus is a friend of Will Herondale, and aids him - and the other Shadowhunters - with various problems they encounter throughout the series. Magnus was said to take a liking towards Will Herondale. His past is also mentioned in The Mortal Instruments.