"Toxic Gas" is an unofficial name for a green, gaseous entity that is an unused enemy in Metroid Fusion. Whether it is a creature, or perhaps even an environmental obstacle is unknown; as it was never programmed with any vulnerabilities. Because of this, Samus is not able to harm or disperse it with any of her Beams, Missiles or other attacks. If the gas cloud is attacked, it will retaliate by creating a group of small explosions around it that do minor damage to Samus. Contact with this possible life form causes no damage to Samus. It is one of a small number of unused creatures in Fusion.