Axel Mortmain (1803-1878 aged 74/75), also known as The Magister, was the adoptive mundane son of late Warlocks John and Anne Shade and is the main antagonist of Cassandra Clare's book trilogy The Infernal Devices, the prequel series to Clare's other series The Mortal Instruments.
Axel was born sometime in 1803 to two unknown mundanes but was raised by two warlocks John and Anne Shade in York, England. As a young child, Axel was shown by John, Automatons he built to protect Downworlders from Shadowerhunters (who at this time would hunt Downworlders) and said that he would rule a clockwork Kingdom and Axel would be its prince. Sometime after 1815, John and Anne were killed by the Clave as they were accused of having unnatural and illegal dealings with demons and creating a weapon that could destroy Shadowhunters. Axel was able to escape this attack with the help of faeries that lived nearby and hid him until the Shadowhunters gave up looking for him.
Axel later tried for recompense through the York Institute as he wanted the Shadowhunters responsible for his adoptive parent's deaths to be tried and punished. But Aloysius Starkweather (one of the Shadowhunters that killed the two) refused his trial.
Since then, Axel plotted his revenge against the Shadowhunters, seeing the whole race responsible for John and Anne's deaths by creating a new race, a form of Warlocks that were half-demon and half-Shadowhunter that would be superior to the Nephilum and cause their destruction.
Axel sent a demon disguised as a mundane man named Richard Gray to make Richard's wife Elizabeth (really a Shadowhunter born as Adele Starkweather and was Aloysius's granddaughter) pregnant with a half-demon/half-Shadowhunter child sometime before or in 1862. Usually children of Shadowhunters and demons are stillborn but Elizabeth was an unmarked Shadowhunter and that she wore a clockwork angel pendant containing the soul of the Angel Ithuriel which kept the child alive and the child was named Tessa. Before Tessa's birth, Elizabeth, her adoptive sister Harriet, Harriet's son/Elizabeth's adoptive son Nate and the real Richard left London for America to escape Axel.
Sometime before or during 1878, Axel was contacted by Nate who had found out about his family's connection to Axel and attempted to blackmail him but instead, Axel invited him to come to London and after finding out about Tessa (now 16), he decided to use Nate's anger and connection to her (as Nate had come to dislike Tessa after finding out about her demon heritage) to his advantage. He had Nate bring Tessa to London and employed the Dark Sisters Mrs. Dark and Mrs. Black to train her to Change.
He also went under the guise of a mere mundane aware of the Shadow World through his membership to the Club led by "The Magister", a vampire named Alexei de Quincey.
Angered at Tessa's escape from the Sisters, Axel left Nate at the mercy of de Quincey, believing his use to be flawed. After been rescued by Tessa and the Enclave, Nate still eager to prove himself, contracted Axel and helped him infiltrate the London Institute. Whilst the older Enclave members went to de Quincey's hideout, Axel told two of the Institute's wards Will Herondale and Jem Carstairs of de Quincey's plan involving a ritual to raise a clockwork army performed by Mrs. Dark. The two Shadowhuters left for the location Axel told them about, leaving the Institute and its inhabitants defenseless. Axel and his automatons came to the Institute and attacked (after getting it due to an automaton with Jem's blood as only those with Shadowhunter blood can enter) with Axel revealing himself to be the true Magister.
Tessa, Sophie Collins and Jessamine Lovelace hid in the Institute's Sanctuary but were tricked into opening the door by Axel who mimicked Will's voice. He had Nate and the automatons take Jessamine and Sophie away, leaving him and Tessa alone in the Sanctuary. Axel tried to convince and coax Tessa into changing into John via his watch (as Tessa had been trained to change into people when in possession of an object of theirs). Not wanting to give in to his commands, Tessa threatened to kill herself, going as far as to change into a woman who had been shot and faked her death.
Believing Tessa to be dead, Axel grieved of the being he had waited years to have. When Will arrived, Axel fled the Institute with his teleportation ring and left behind a button from his jacket which Will cut with his seraph blade. Though later learning that Tessa was alive, Axel did succeed in retrieving a Pyxis (which stored demon energy) which carried the Greater Demon Armaros from the Institute through Nate.
Using the demon energy, Axel was completely successful in raising his clockwork army and made them resistant to the Shadowhunters seraph blades and also bound them to his life. He later captured Tessa and forced her to watch the automatons attack a nearby village. However, near the end of the book, Tessa (using her clockwork angel) changes into Ithuriel and picks up Axel and crushes and burns him to death, leaving nothing but his bones.
- Axel was in his mid-70s, but looked younger due to dark magic.