Xenon is a corruptive substance that has plagued the galaxy for millions of years. It is incredibly destructive, although to those who can survive it's generally deadly effects, it has been known to mutate and provide an immense increase in strength to them. It has also been known to eventually claim the minds of nearly everyone it has possessed in this way, turning them into mindless slaves.
Xenon was originally created by one known simply as The Dark Lord. Very little, if anything, is known about this shadowy figure. Slatenin, a Xenon minion, claimed to be the Dark Lord, but it has been confirmed by Xenon still spreading after his death that he was not. The Dark Lord is rumored to still govern Xenon, although this is debatable.
Xenon has claimed the minds and lives of many famous warriors, races, and even planets, including:
http://www.submiturpics.com/images/utjg159997r018yxlhz.png (a closeup of Xenon in it's purest form)