Tartarus

Tartarus is a place within each and every planet. Every Planet.

Deep within each planet, was thought to be an impenetrable, smooth, stone protecting it's core. When scientists finally figured out how to break it, what they discovered was a large massive 'cave' system of pulsating organs.

Their next discovery was resources incredible for technological development, and they sooned caved out all of Zenith, Ultimately leading to it's destruction. But luckily for the concept of 'Tartarus', there are other Tartari out there. In each planet, waiting to be discovered.

It's quick to drive those who stay there mad.