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Asteroidea 472A is a compound which exist in a solid form under certain conditions, but will vaporise in an Earth-like environment. In its gaseous form it is highly-dangerous, capable of liquefying the human body almost instantly if inhaled. Even in a lower concentration it is still dangerous, and considered worse in this manner as infected humans are forced to die a painful death after several hours.

In 2557, researchers on the UNSC Argent Moon experienced a leak while experimenting with this compound. It quickly made its way into the ship's ventilation and successfully killed the entire crew.


  • Asteroidea is the taxonomical name for the Starfish family.