Level 16: The Omen
Back to Final Doom
From the Start head down the stairs and take out the Revenants and other enemies. The slime pool is not damaging. You’ll find a Backpack to the right of the steps and a BFG in the corner.
Lower the lift to the south so you can get past to the southern side. Take out the Specters and then grab the Blue Key. When you do have your BFG ready to take out the Mancubus and Revenants that spawn in.
Ride the lift up and follow the walkway to the north. Clear out the enemies and grab the Red Key at the end of the walkway. More Revenants and Hell Knights will teleport in once you grab the key so be ready to retreat.
Now that you have both keys drop down into the Starting area and open the Blue Door. Kill the Specters and Reventants in the room beyond and grab the Yellow Key. Watch out for the 2 Arch Viles that spawn in behind the cage in front of you. They’ll quickly teleport out and be much harder to deal with.
Go back to the room where you picked up the Blue Key and open the Yellow Door to the east. It’s filled with Chaingunners so you may want to clear them out quickly with the BFG.
To get to the Exit ride the pillar up on the right and open the Red Bars. Press the Button and drop back down. A pillar will have lowered with a teleporter on it. step into it to be taken to a room with slime walls. Step into the Exit to complete the level.