The Timeless Child storyline was perhaps the most controversial aspect of Chris Chibnall's tenure as Doctor Who showrunner. In this plot thread, the Thirteenth Doctor learned that she was not originally from Gallifrey, but that she had been discovered as a child by a Gallifreyan woman named Tecteun, who took her in and raised her. This unknown child possessed the power of regeneration, and it was through them that the Time Lords learned those secrets. Unlike other Time Lords, though, the Timeless Child could regenerate infinitely. The Doctor has actually had many more than thirteen forms, but the Thirteenth Doctor couldn't remember all of her previous regeneration cycles.