These spiders were domestic spiders that had grown to a giant size thanks to science and a toxic landfill site full of garbage.
The spiders continued to follow their natural hunting instincts, however, confused by what had happened to them, they began hunting humans.
The Thirteenth Doctor, Graham, Ryan and Yaz encountered the super-size spiders on Earth in Sheffield. Tracing them back to a posh hotel, they discovered the spiders weren’t evil at all, but the victims of American businessman Jack Robertson’s dodgy scheme. Robertson had built the hotel on toxic landfill, where spiders which had been scientifically experimented on were being disposed – and the toxicity from the landfill had caused them to grow supersize.
The Doctor and her friends were able to lure the spiders into a secure room using the vibrations of Ryan’s grime music, saving the population of Sheffield – and potentially the Earth! – from this eight-legged infestation.