Magnus Crome was born on London in 936 TE. He was raised by the Guild of Engineers in the Deep Gut nurseries, during which he read about the dwindling amount of prey and that traction cities were doomed. Deciding to make it his life's work to keep tractionism alive, Crome acquired his guildmark and climbed the ranks of the Guild until becoming the Chief Engineer. During his time as Chief Engineer he strengthened the Engineer's power through increasing the number of seats it held in the city council. Crome was also a firm believer in Municipal Darwinism - once claiming to be descended from Dr. Gideon Crumb.
Before Mortal Engines
In the aftermath of the Big Tilt of London of 997 TE, Lord Mayor Waverley Egg was ousted from his position due to the ensuing scandal and gave rise to Crome's election - though some believed that Crome had caused the Big Tilt himself to attain more power. Crome enforced fierce anti-waste and recycling laws to help keep London moving.
Differently from past Lord Mayors, Crome did not have his guildmark removed, not even wearing the typical red robes required of a Lord Mayor - preferring to wear the Engineer's white rubber coat. Many objected to Crome still being the Chief Engineer whilst acting as Lord Mayor, though they themselves admitted Crome was an exceptional leader.
Crome was a firm supporter of Thaddeus Valentine, whom he made into the Head Historian after the archaeologist discovered the super-weapon MEDUSA; the Engineers began work implementing the weapon into St. Paul's Cathedral. Realising that this weapon would give London an advantage in the waning years of tractionism, Crome, under the guise of looking for more prey east, ordered his city to move over the Land Bridge and into the Great Hunting Ground. The Lord Mayor intended to use MEDUSA to destroy the Shield Wall of Batmunkh Gompa, allowing passage into Shan Guo and the innumerable resources there.
A year and a half before the events of Mortal Engines, the Stalker Shrike boarded London and was captured by the Guild of Engineers. Crome had Dr. Evadne Twix, the head of K Division, study Shrike in order to make Stalkers as foot-soldiers for London. Shrike warned Crome that Hester Shaw, the daughter of archaeologist Pandora Shaw (and Valentine's former lover who originally discovered MEDUSA), would be coming to London to assassinate Valentine in revenge for her parents' murder. In return for studying Shrike's components, Crome would allow Shrike to bring Hester's body to the Engineers and turn her into a Stalker companion for him.
Giving the order to chase a small mining town called Salthook after crossing the Land Bridge, Crome presumably witnessed the town being eaten. He later visited Valentine after an incident with Hester. Crome sends Valentine to scout ahead in his airship the 13th Floor Elevator, to see what lies between London and the Shield Wall. Valentine wants to try and find Hester, but Crome tells him that he is sending an "agent" to track her down.
Crome then returns to the Engineerium, the Guild of Engineers' headquarters, and meets with Twix. The pair then visit the imprisoned Shrike, and Crome informs him of Hester's boarding of London. Shrike demands to go after her, and Crome agrees, supplying him with a Godshawk 90 airship.
Crome was described as being as "thin as an old crow, and twice as gloomy", with a shiny bald head and the common Engineer guildmark of a red wheel on his brow. Crome elected not to wear the typical scarley Lord Mayor robes, still wearing his white Engineer rubber coat.
Crome was an exceptionally intelligent Engineer and Lord Mayor, managing to keep London moving as it was isolated from the Great Hunting Ground. Despite this, he was exceptionally proud and ambitious, wanting to "make London strong", showing that he was fanatically patriotic to his home city.
Typical of an Engineer, he valued his guild above all others and strove to strengthen its hold over the city. Crome was quite a workaholic, ensuring meetings took place at the exact time specified and making sure that nobody knew of his secret plans.
Despite this, during his final moments in St. Paul's Cathedral before MEDUSA backfired, he broke down and sobbed, likely due to his plans failing - suggesting that he believed his intentions were good and honourable for the traction city.