Timeless Child

The "Timeless Child" was a truth hidden by the Time Lords. A secret too devastating to learn, the discovery caused the Spy Master to ravage Gallifrey, apparently killing off the Time Lords. (TV: Spyfall) Remnants referred to the Timeless Child when drawing on the Thirteenth Doctor's fears and history, on the planet Desolation. When the Remnants made the reference, the Doctor was stunned for a moment before she angrily told the Remnants to get out of her mind when they taunted her. (TV: The Ghost Monument)