|“||Beware, Nephilim. As you slay others, so shall you be slain. Your angel cannot protect you against that which neither God nor the Devil has made, an army born neither of Heaven nor Hell. Beware the hand of man. Beware.||”|
–Automatons, Clockwork Angel
Automatons are mechanical "clockwork" creatures made to move and appear like human beings. They were used by the Magister to form a clockwork army that would destroy the Shadowhunters.
The concept of these automatons were based on the idea first suggested by Leonardo da Vinci. In the 1800s, the warlock John Shade and, much later, his adoptive mundane son Axel Mortmain expounded on this idea and dedicated decades to the research and experimentation to perfect automatons. Separately, they were successfully able to create true biochemical automatons which were self-moving, self-directing, and made up of mechanical tools wrapped in actual human flesh, taken from bodies of their murdered victims.
Attacking the Enclave
The Sisters kept two automatons in their home: their maid, Miranda, and their coachman, both of whom Tessa Gray met during her time there. Because of the peculiar way their eyes protruded, Tessa assumed that they were related. The House's cellar also served as a storage and production unit for some of the automatons—specifically, some of the parts (both mechanical and biological) were stored there. Miranda was at one point ruined after Tessa attacked it, and she was later found by Will Herondale and Jem Carstairs barely functioning. She was taken back to the London Institute and was cut open by Henry Branwell to study.
The clockwork creatures later tried to take Tessa captive again while she was at the Blackfriars Bridge with Jem under orders from Mortmain. One of them brutally attacked Jem for some of his blood, to be used later to gain access to the Institute.
During a battle in a tea warehouse, Tessa Changed into her brother, Nate, so she could command a large automaton, which only obeyed her brother's voice. Will threw one of Henry's inventions at it, which caused it to short-circuit and explode.
Mortmain created an automaton with Mrs. Black's head attached to it to capture Tessa, though he later destroyed her in an attempt to win Tessa's favor.
Mortmain used a spell created by his father to capture the demon souls he took from the Pyxis and trap them in the automaton, and tested by sending them to attack a mundane village. He later sent them to London to attack the Shadowhunters during a Council meeting. These newer models of the automaton were enhanced with magic and demon energies. With these improvements, the automatons were made invincible to runed weapons and seraph blades of the Shadowhunters.
The Shadowhunters of the London Institute fought the automatons at Cadair Idris, where many of them were destroyed with one of Henry's inventions, which worked similarly to a Pyxis.
An automaton, animated by the demon Armaros' life force, kidnapped Tessa from the fight with the automatons in Mortmain's lair, and held her hostage in front of the Shadowhunters. However, before the automaton could take her to Mortmain, Tessa Changed into the angel Ithuriel. Tessa/Ithuriel killed Mortmain, which resulted in the destruction of all the automatons.
Most of the automatons Mortmain created lacked organs and other body parts such as bones, cartilage, and hair; others even lacked facial features. But while ordinary automatons would normally have no individual creativity or imagination, aside from those programmed into them, the later model the Magister had created were animated by demon energy, giving the automatons a measure of thought and will; the demons from whom the energy was harvested were bound and enslaved to their creator in exchange for new automaton bodies.
- The automatons were the central source of conflict and the titular topic of The Infernal Devices.