Cheat Codes In Doom Eternal are neat little tools to help grab missed collectibles in missions you have already completed or to just experiment with weapons using infinite ammo and more. They're a great way to incentivize players to replay missions and don't at all affect progression, so there's no penalty for using them (other than Slayer Gates locking while they're enabled). Use them, that's our pro-tip. So, let's go over what each one does and where it can be found throughout Doom Slayers' quest to slap every single Demon across the mouth.
15 Hell On Earth: Infinite Extra Lives
The first one is of course, in the first level. Most players probably stumbled upon it themselves. But, just in case you didn't, all you have to do is play through the intro level naturally until you first encounter the tentacles that randomly pop out of the floor. Once you get to the other side of that corridor and before you go up the stairs, look around for a box, hop on top, get into the vent, follow it around, and there you go! This cheat quite obviously gives Doom Guy infinite extra lives, though respawning right into another attack is one of the things the game needs to fix soon.
14 Fortress Of Doom: All Runes
Most of the Cheat Codes are found throughout missions, but there are actually two of them hidden in Doom Guy's central hub, the Fortress of Doom. This one is only accessible once the ship is "powered" enough for you to access the auxiliary room that is separated by a bridge. Once you get to the one that has the original Prateor Suit floating in it, jump out the hole in the wall and wall, turn back around, and dash into a cubby about 3/4ths of the way down. In it is this cheat code which, like the name suggests, turns every single Rune on at once.
13 At Any Time: Activate All Cheats
This one's quite simple and actually requires no work on your part. So, as the title suggests, this cheat code simple activates all the cheats at once! It's an on-off switch for the entire cheat code page just in case you don't care about which specific ones you want on while revisiting an old level.
It unlocks automatically as soon as you collect the first Cheat Code as if to say, "yeah you got one, so now this option makes sense to even include".
12 Fortress Of Doom 2: Fully Upgraded Suit
This is the second of two FoD Batteries that are locked behind story progression. So, this next one can't be accessed until a returning character "inhabits" your Fortress, you'll get it when you get there. Once that's happened, Look at the stained glass windows near the ceiling in the room that holds the Crucible Container (the glowing red thing with a sword hilt in it). Shoot the red target on one of the windows, which turns on a Grav Lift near the container. Hop on that bad boy and ride it all the way to where the cheat code is resting.
11 Cultist Base: IDDQD
This next one is found in the second Level called "Cultist Base". Fight your way through the hordes until you get to a room full of cages you can open by melee'ing the chains. Look for a cage with the collectible question mark inside. Once you've found it and cleared the room of all Demons, approach from the side that the bars are located on, swing from one of the yellow bars on the left or right, then turn around and dash into the cage in mid-air. Easy peasy.
10 Doom Hunter Base: Silver Bullet Mode
The Silver Bullet Cheat Code is found in the Doom Hunter base and it's tough to explain its location.
It's around the area where you're scrambling from wall to wall and the floor has that red lightning on it. Basically, once you enter a room after slamming the green skull switch into place, you're about there. Keep climbing on walls until you can jump to the central pillar and Viola! This code simply ax's any Demon that is shot while staggered.
9 Super Gore Nest: Infinite Ammo
Ah, here we are, back to a location that is simple to explain. Near the end of the level, you'll be asked to slot keys into the Gore Nest. Before you do that, turn and jump onto the destroyed building platform. Then, from there, turn back towards the Gore Nest, and you'll notice a wall you can melee a bit further down. Hop off, wait for the right timing, slap that wall open, dash in, and grab the code! Again, another obvious one, this just gives Doom Guy infinite ammo whenever it's enabled.
8 Arc Complex: IDKFA
Again, this is another code we've noticed players stumbling across naturally. The collectibles in Doom Eternal aren't all that hard to find, there is just a lot of them. In any case, keep your eyes open until you swing off a bar into a room that sort of looks like a Laundromat. Once you clear the demons out simply look for a small hole in the floor and you're good! And, the IDKFA unlocks all weapons and powers them up to fully mastered whenever its equipped
7 Mars Core: Powerup Mode: Infinite Onslaught
Ooh! Another easy description. So, wait until you fire yourself from a literal cannon (one of the most badass things Doom Guy's done) into a building. Right after that, clear out the room and go down the stairs. You'll see another Grav Lift in here, ride it up and grab the code. The Infinite Onslaught code is another self-explanatory one that simply turns Onslaught on and it never runs out while equipped.
6 Taras Nabad: Powerup Mode: Overdrive
Taras Nabad is a pretty difficult stage, but just wait until you have a combat arena in a small room. Once you clear that out, head up the stairs in the room and head to the left.
After this, all it takes is finding a breakable wall, smashing it to bits, and following the path to knab the second of three Powerup-based cheat codes right next to a Slayer Gate. Same purpose as the last one, except with the Overdrive effect.
5 Nekravol: Famine Mode
The next stage is a real long one, and actually has three different cheat codes spread throughout. The first one is found right after you fight a Maurader, look around for cages holding corpses that are moving up and out of the room. Wait for a break in the cages you can fall through, then grab the code. Famine Mode is one of the rare Cheats that actually make things harder like Halo Skulls, Demons no longer drop Armor or Health on death with this on.
4 Nekravol 2: Party Mode
And, speaking of Halo Skulls, this next cheat code also does something similar. You'll want to keep progressing until you have to drop down a large shaft. Looking down said hole, look for a tiny ledge on the left you can land on. Then look for a breakable wall, break it like you mean it, and grab the code on the other side. Sometimes its easy to fall off, so you might have to fast travel back up foranother try. The Party Mode Cheat makes Demons burst into confetti when killed, just like the Grunt Birthday Party Skull.
3 Nekrravol 3: Instant Stagger Mode
The last one in this left is just before you break the chains of the Titan. Turn around, look for the elevator you rode, and hop down the empty shaft. While falling, quickly turn around and dash into an opening, it'll be close to the bottom of the shaft. Right inside is the code. Simply put, this staggers all enemies well, instantly (except for bosses).
2 Urdak: Powerup Mode: Berserk
Now we've arrived at the last of three Powerup Codes, in the Urdak mission you have to align a couple of rings blue, yellow, and purple. Right after the purple one, in particular, head outside and look behind you and to the left. You'll see yet another breakable wall you have to jump to reach. Jump, smash, and grab the Berserk code for the new ability to rip demons apart instantly.
1 At Any Time: QuakeCon Mode
And lastly, we're capping things off with a Cheat Code that can't be found anywhere. No, instead of being discovered through exploration of the environment, it's found through maxing out one of the seemingly endless skill trees. Particularly the Praetor Suit upgrades in the redundant "Suit" tab of the pause menu. Max out all these upgrades and you'll unlock the QuakeCon Mode cheat which does nothing useful but puts a fake audience in that cheers and hollers based on your performance. How very Devil May Cry