The first level of Doom Eternal, Hell on Earth, features 13 total collectibles to find. You'll be going through the Barge and City sections of the map, slaying demons along the way while learning the ropes. In total, you'll find:
- 3 Modbots
- 6 Codex Pages
- 3 Toys
- 1 Cheat Code
All Collectibles in Doom Eternal Hell on Earth
Right after you get the Chainsaw, there will be a breakable wall on the left. Punch through said wall and follow the tunnel until you drop onto the Zombie Toy.
Unmissable. Punch the cube and jump up. It will be next to the door.
Codex: Hell Barges
Unmissable. Codex Entry: Hell Barges is located in the hallway after you clear out the room with the two jump pads.
Codex: Remaining Human Populations Pt. 1
After the cutscene where you meet the first Hell Priest and acquire his head, jump down. Codex: Remaining Human Populations Pt. 1 will be on the exterior corner of the building in front of you on the edge of a cliff.
Unmissable. Located after you jump into the ruined building next to the Codex Entry: Remaining Human Populations Pt. 1.
Doom Slayer Toy
After acquiring the second Modbot, you will have to punch a wall to progress. Immediately after punching the wall, jump up and go to the left to find the Doom Slayer Toy.
Eventually, you will come across the Scott building. Outside of the Scott building, there is a wrecked truck. Jump onto the truck and then jump onto the ledge above the ShuZ building sign where an Imp is standing. The wall on the left can be punched, letting you drop down onto the Imp Toy.
Codex: Remaining Human Populations Pt. 2
After you get the Imp Toy, go left. The floor has collapsed, but you can walk on the ledge to the right next to the windows until you get to the other side of the room. There will usually be an Imp minding his own business next to Codex: Remaining Human Populations Pt. 2.
After you make it past the second set of wall blasters, you will find yourself in a wrecked subway station. The bot will be on the subway platform between two subway cars, next to the door that you're supposed to go through.
Codex: Formation of the ARC
After you climb up the collapsed train, Codex: Formation of the ARC will be at the end of the tunnel.
Cheat Code: Infinite Lives
Before you walk past the third tentacle hole in the subway, look to the right, in the opposite direction of where you're supposed to go. There will be some boxes that you can jump onto which will lead to a vent. Punch the grate and Cheat Code: Infinite Lives will be right in front of you.
Codex: Hell Priest
After you enter the portal to the demonic temple, you will have to make your way inside to the skull button to activate the elevator and end the mission. Before you press the skull button, look behind the skull button (opposite of where the skull is facing) to find Codex: Hell Priest.
Codex: Deag Nilox
On the right side of the aforementioned skull button room, you'll find Codex: Deag Nilox.
After you finish the level, you will be transported to the Fortress of Doom. Acquiring the Sentinel Crystal is a marked objective, and thus can't be missed.