Mylon was a heavily fortified refinery planet that was used by Nefarious as a Biobliterator fueling plant and the place where Nefarious had his primary base for operations in Up Your Arsenal. It was the final planet in Ratchet & Clank: Up Your Arsenal. Opposed by dozens of robot Tyhrranoids and robotic minions of Nefarious, it was where Ratchet and Clank bravely fought their way through the base and eventually reached the Biobliterator and Nefarious, and defeated the evil scientist, destroying his Biobliterator. The climate on this planet appeared to be polluted, muddy, and dark, due to all the refineries and fueling stations. The sky was a dark brownish color, just like planet Umbris.