Unfinished Doom 3 monsters

http://images.wikia.com/doom/images/e/e6/Mastermind.JPG

In DOOM3 there were many unused demons, such as the spider mastermind. These demons never showed up in the game or in a cutscene. Reasons why for right now are unknown.

http://images.wikia.com/doom/images/c/c5/Concept_artness.JPG