Collectibles Mission 11

Elite Guard #1: Hard to miss. After dropping down a long way and defeating a couple of Cacodemons in the area below, hop over the floating platforms until you reach a tunnel. The Elite Guard is at the very beginning.

Mission 11 - Elite Guard #1

Elite Guard #2: Near the end of the mission you'll be in a hall with several Spectres and Barons of Hell. At the end of the hall you'll find this Elite Guard lying against a wall in a room.

Mission 11 - Elite Guard #2

Classic Map: After the first big fight and after collecting the Yellow Skull, look for the lever in one of the corners with fire. Head back the way you came (towards the Argent Cell) to find this map on the right side.

Mission 11 - Classic Map

Argent Cell: After going downstairs at the beginning of the mission, turn left and go up the steps to find this Argent Cell in plain sight.

Mission 11 - Argent Cell

Tealguy Collectible: After dropping down a long way down, kill the Cacodemons and move over the floating platforms to reach the start of a tunnel. Turn around and check the small floating platform slightly to the lower right. This collectible is on it.

Mission 11 - Tealguy Collectible

Hazmatguy Collectible: Right before the end of this mission you'll spot a large demon skull with a red glow on its forehead. Shoot a rocket at this spot on its forehead (similar to how you needed to kill the final boss in Doom 2) to release this collectible from it.

Mission 11 - Hazmatguy Collectible