- "Wheel World" redirects here; you may be looking for the Wheel of Misfortune or Wheel Gator of the Mega Man X series.
Argentium, also known as the Wheel World, is the home world of the alien race known as the Bem. It is a massive ring-shaped planetary body with a unique gravity field that enables objects to rest on its inner surface and appears to be a hub of interstellar activity due to the placement of warp gates that allow travelers to come from afar as well as reach far-off destinations. For nearly twelve years this planet served as the adoptive home of Amadeus and Rosemary Prower, who had been brought here by Ceneca-9009 and spared from most of both the First and Second Robotnik War, despite their pleas to the Bem High Council for an intervention on Mobius's behalf. Sonic the Hedgehog briefly visited it during his travels in space to return to Mobius (fleeing after witnessing the trial of Ceneca-9009 and helping her escape), and later returned with Tails, Knuckles and Merlin to rescue the Prowers, only to find the planet the site of a battle in the ongoing war between the Black Arms and the Xorda. Argentium also turned out to be where grey Chaos Emeralds could be found, but the planet was stripped bare of them during the Great Harmony. (StH: #118, #123, #129, #169, #170)