Amnesia

Amnesia, sometimes known as Planet Amnesia or Galaxian III, is a mostly uninhabited planet with an atmosphere composed of noxious gases that tend to cause rapid deterioration of memory and cognitive functioning. It contains both heavily wooded areas and a large canyon with subterranean cave systems. One of these caves was the hiding place of the Phantasm until the SILPS trio discovered it after surviving an attack by the one humanoid species on the planet, the Blackrobians.