Krethus is a planet, home to a bunch of Rouge, malfunctioning, robots.
It is a blue planet slowly being turned metal by it's owners.
Some of Invader Daxlek's robots went rouge and stole some of his tech to create a new home.
The people of Krethus behave like pure robots. They are very agressive, though.
Project Downgrade Edit
Invader Daxlek, worried that the Irken Military would think they are a threat, hired some former Irken Warriors to destroy the planet and BOOM- the deed was done.