Stilton Kael, more commonly known as Uncle, is a recurring character in the original Mortal Engines Quartet. He appeared in both Predator's Gold and Infernal Devices. He spent much of his life in Grimsby as founder and leader of the Lost Boys.
Stilton Kael was born in Arkangel and lived there for much of his youth and young adulthood. When Anna Fang was taken as a slave to work in a junkyard, he fell in love with her. However, Anna Fang only pretended to return the love while she secretly built her airship the Jenny Haniver using parts from his junkyard. When Anna Fang escaped, Stilton Kael was blamed and was said to have let her go. He was exiled from the city into the ice wastes. However, he joined a group of Snowmad scavengers who were bringing salvage from the wreck of Grimsby. After he killed them all, he stole the Naglfar, their spacious cargo submarine, using it to claim Grimsby for himself, make it habitable, and set up the Lost Boys.
When Hester Shaw, Tom Natsworthy, Caul and Freya Rasmussen arrived at Grimsby to rescue Wren Natsworthy, they were captured by Uncle as a result of Caul's betrayal. Uncle had made a portable group of screens that were tied to a balloon, so he could see his Lost Boys wherever he was. Uncle was convinced that the damaged Grimsby would be able to be remade, but Hester, Tom and Freya disagreed. When Freya tried to persuade Uncle to come back to the surface again, he suspected a trick, and shot Freya's face on the screen. However, in doing so, Uncle punctured the balloon holding his screens up, and was crushed beneath his own monitors.
Uncle is described to be a small man in a dressing gown with bunny-rabbit slippers. Though this may appear innocent, the inside of the slippers are capped with steel. He wore half-moon spectacles, and five-cornered hat.