Karl Brian Wright was pursued as a "trophy" by Tim Shaw. He lived at 52 Northover Street, Sheffield and worked for his father's company, Skylark Building Services as a crane operator. He listened to self-assurance recordings to have confidence in himself.
He was on the same train as Grace and Graham O'Brien when a gathering coil attacked it in pursuit of him. The Thirteenth Doctor crashed down into the carriage they were in and managed to scare the coil off with an electric cable. He left soon after.
However, Tim Shaw was still in pursuit of him and tracked him down at Skylark, killing Dennis and Dean on the way. He climbed the crane that Karl was in, but the Doctor, Yasmin Khan, Ryan Sinclair, Graham and Grace prevented him from taking Karl.