Skip to content
Level 21: Mt. Erebus
Doom

Level 21: Mt. Erebus

Your Doom walkthrough for Level 21: Mt. Erebus. Learn how to navigate the lava pits, find hidden doors, and grab the Yellow and Blue Keys to escape.

By ···10 min read·Multi-source verified
1 reading this guide  

Your Doom walkthrough for Level 21: Mt. Erebus. Learn how to navigate the lava pits, find hidden doors, and grab the Yellow and Blue Keys to escape.

Alright, welcome to Level 21, Mt. Erebus! This one can be a bit of a maze, but stick with me and we'll get through it. It’s time to conquer this icy peak.

Walkthrough
  1. 1
    You'll start the level and immediately want to head left. Don't fall in the lava! Cross it carefully.
  2. 2
    Once you're across the lava pit, look for an opening directly across from you. It should be on the opposite side of where you crossed. Head into that opening.
  3. 3
    Inside, turn right. You'll see another opening across from you. Go up to it and turn right again.
  4. 4
    Now you should see a green wall in front of you. Walk up to it and turn right. Follow this wall until you find a door. Open it and go inside.
  5. 5
    This room is filled with Zombiemen and Shotgun Guys. Take them all out.
  6. 6
    Once the room is clear, turn left and face the walls. Look closely – you should see a small candle in front of the walls. This is a hidden door! Open it and go through.
  7. 7
    Inside, you'll find a teleporter. Step into it, and you'll be zapped outside.
  8. 8
    Once you're outside, you'll see four openings leading back into the building. One of these is a switch. Hit it! This will open a door back into the building. Go through it.
  9. 9
    In this new room, you'll face Imps, Shotgun Guys, and Demons. Clear them out, then head to the other end of the room and hit the switch there.
  10. 10
    After hitting the switch, turn around. You'll see that parts of the wall have opened up, revealing some more enemies and, importantly, the Yellow Key! Grab it.
  11. 11
    With the Yellow Key in hand, leave this room. Back outside, find the Yellow Door and go through it.
  12. 12
    Inside, you'll find another teleporter. Step on it, and you'll be transported to a Y-shaped building.
  13. 13
    Once inside the Y-shaped building, turn around and follow the hall. You'll come to two openings. Take the one on your left.
  14. 14
    The wall in front of you will lower, revealing more Imps and the Blue Key! Grab the Blue Key.
  15. 15
    Turn around, then go back to the other opening you passed. Hit the switch in front of you there.
  16. 16
    Now, turn around again and go through the opening to your left. You'll need to drop down to the floor below.
  17. 17
    Once you're down below, turn around. Follow the right-hand wall until you see a lava pit off to your right.
  18. 18
    Enter the lava pit. Yes, really! Go through the opening to your right within the lava.
  19. 19
    Follow this short hall, and you'll find the Blue Door. Open it and go through.
  20. 20
    Finally, you'll see the exit door. Open it and step through to finish the level! You'll then step on the exit teleporter.
Tips
  • Keep an eye out for hidden doors – that candle trick is just the first of many secrets you might find in Doom!
  • Don't be afraid to use your shotgun on the Shotgun Guys; they can be dangerous in groups.
  • The lava looks scary, but sometimes you just have to walk through it to find the path forward. Just be ready to grab the key and move!

100% Human-Written. AI Fact-Checked. Community Verified. Learn how AntMag verifies content