Centre of the Earth

The Centre of the Earth, also referred to as Earth's Core, was where lizard people resided. (PROSE: Teddy Sparkles Must Die!) By one account, the Centre of the Earth was the Secret Heart, a Racnoss ship that was the centre of the Earth. (TV: The Runaway Bride)

History
Teddy Sparkles once took Esme, Jack, and Peter to the Centre of the Earth where they faced flesh-eating lizard people and exploding volcanos. Missy reluctantly saved them while riding on the back of a giant Robot Badger. (PROSE: Teddy Sparkles Must Die!)

The reptile people raged against the Ape Primitives who had stolen their planet from them. They were encountered by Iris Wildthyme, who had to stop MIAOW from committing genocide on them. During the same adventure, she also came across a dashing old gentleman resembling Peter Cushing. (PROSE: From Wildthyme with Love)

During the 22nd century, the Earth's core became the target of the 2150s Dalek invasion of Earth. Having located a fissure in the Earth's crust with optimum potential for Project Degravitate, the Daleks set their human slaves to excavate a tunnel at a mine in Bedfordshire. When complete, an explosive capsule was to be sent down the shaft to strike the fissure in the Earth's crust, releasing the molten core. The Daleks then planned to control the vast release of energy and replace the core with a propulsion system that would allow the Daleks to pilot Earth anywhere in the universe, (AUDIO: The Dalek Conquests) only for the First Doctor to stop their plans. (TV: The Dalek Invasion of Earth)

During the Daleks' second invasion in the 2180s, they again attempted to replace Earth's core, this time installing a time warp engine only for the Eighth Doctor to stop them. (AUDIO: Lucie Miller / To the Death)