02 March 2023

What is the Medusa weapon in Mortal Engines?

The Medusa weapon is an ancient Old-Tech super weapon that appears in the Mortal Engines book series. Magnus Chrome, the Mayor of London City, attempts to use it to breach the Shield Wall and gain access to the fertile hunting grounds beyond. 

The Medusa is a 'ground-based' weapon, taking up the whole of the inside of St Paul's Cathedral, where the Guild of Engineers rebuilt it under complete secrecy. It has a huge, metallic hood shaped like a cobra's hood and fires a beam of energy, resembling a "cat-o-nine-tails", at targets up to two hundred miles away. Firing coordinates are input via a control panel at the base of the firing mechanism.

The Medusa was never used as intended in the book, as it was accidentally destroyed by Katherine Valentine who was mortally wounded during her noble attempt to sabotage it. 

The weapon was originally deployed in America during the Sixty Minute War, which turned planet Earth into a post-apocalyptic wasteland from which traction cities eventually evolved. 

medusa mortal engines

London secretly made archeological expeditions to the Dead Continent and gathered the pieces of Medusa from an old Brothal base and reassembled it inside the St Paul's complex. 

Thaddeus Valentine, working for Magnus Chrome, had previously tracked down the computer control system of the Medusa, which was in the hands of Hester's parents. Valentine killed them and scarred Hester with his sword, both physically and mentally.

In the book, Katherine Valentine spends most of the first part of Mortal Engines trying to figure out what the Medusa is. During the chase of London by the city Panzerstadt-Bayreuth, the roof of St Paul's Cathedral lifts up and destroys the predator city with a blast of pure energy from the weapon. 

The successful use of the weapon serves as proof of concept to Magnus Chrome and adds to his resolve to breach the Shield Wall. However, Magnus' plans are foiled when the Medusa system overloads with energy and explodes, obliterating most of London with it.

The movie version of Mortal Engines has some differences from the book, as Medusa is actually fired on the wall before it is destroyed by Tom. Nevertheless, the weapon remains a crucial plot point in the book series, with its destructive power serving as a stark reminder of the devastation caused by the Sixty Minute War.
Jimmy Jangles

Founder & Editor •  |  @JimmyJangles

Jimmy Jangles is an independent science fiction analyst and media critic based in New Zealand. He founded The Astromech to dig into the themes, mythology, and ideas behind the stories that shape how we imagine the future — from Star Wars and Dune to Alien, Star Trek, and beyond. He also runs How to Home Brew Beers.

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