Earth's core

Earth's core is a turmoil of superheated rock known as magma. It is potentially a source of immense power, provided it can be safely tapped. Accessing Earth's core can be a tricky prospect, however should you try, be very careful what you're getting into.

The Transformers cartoon
A shaft of crystal in the Arctic led all the way to Earth's core. The Decepticons tapped it to turn Earth's heat into energon, causing temperatures worldwide to plummet. After a battle with the Autobots resulted in the Decepticons retreating, the crystal was buried.

Another similar crystal shaft was located in Peru. The Decepticons used the energies from the Earth's core to power a laser cannon until the Autobots again foiled their plans.

Never ones to give up, the Decepticons constructed a massive drill in a cave and began drilling their way to the Earth's core. This plan was undone when an Autobot attempt to gain control of Devastator resulted in the giant damaging the drill, endangering Earth while the Decepticons were still on it. Devastator successfully stopped the drill before Earth was destroyed.