Caco-Spectre

Caco-Spectre is a rare yet unique variant of the Cacodemon, and one of the few monsters encountered exclusively in the Sony PlayStation port for the classic Doom. Similar to the Demon's nearly-invisible cousin Spectre, the Caco-Spectre is well transparent but has an identical sprite, along with same exact behavior and attributes.

Nevertheless, there is only one enemy. It is located in the PlayStation version of "The Tenements" level (MAP45), due to this monster having the same flag as a Spectre demon. The creature is found inside a cage above a pit of brown nukage, replacing the Arch-vile who appeared in MAP17: Tenements from the original computer ports. Although while it is very likely that the player can kill the creature without approaching it, players has no chance to notice its transparency.