Mars Core

Doom Eternal missions
Hell on Earth Exultia Cultist Base Doom Hunter Base Super Gore Nest ARC Complex Mars Core Sentinel Prime Taras Nabad Nekravol Nekravol - Part II Urdak Final Sin Fortress of Doom (hub)
The Ancient Gods, Part One
UAC Atlantica Facility The Blood Swamps The Holt ARC Carrier (hub)
The Ancient Gods, Part Two
The World Spear Reclaimed Earth Immora The Dark Lord

Mars Core is the seventh level of Doom Eternal. After learning from Samuel Hayden that Deag Grav, the final Hell priest, is on Sentinel Prime, the Doom Slayer must proceed to Mars to locate a trans-dimensional gateway to Sentinel Prime, hidden in the planet's core within the lost Night Sentinel city of Hebeth. As VEGA confirms there are no pathways leading there, the Slayer travels to Phobos to gain access to its BFG-10000 orbital defense system and blast a hole in Mars directly to the core.

The BFG-9000 weapon is found in this level. The Maykr drone enemy is also introduced in this level via the Slayer Gate. It uses the music tracks "Mars Core", "Phobos Space", "Asteroids and Rockets", "You Can't Just Shoot A Hole Into The surface of Mars", "Command and Control", "BFG 10k", "Phobos Base", and "Aquiring the BFG".

"With the help of Samuel Hayden, the final Hell priest has been located on Sentinel Prime—a city from your past. The only known path to this now accursed place is through the dimensional gateway hidden in the core of Mars, wherein the lost city of Hebeth resides. The journey there will take time you can't afford to waste—a dilemma which calls for a more...direct approach."

― Loading description

Lore

Originally established as a mining and communication relay, the UAC outpost on Phobos was expanded following the destruction of the Argent facility on Mars at the request of the UAC's board of directors, who wished to retain their monopoly over the planet. The expansion plan included the addition of a BFG-10000 particle cannon; derived from BFG-9000 technology, this would become the largest man-made weapon platform ever conceived.

The city of Hebeth once bridged a number of disparate Sentinel cities thanks to its slipgate, but was lost in the crusades of the ancient Sentinels. Its ruins have since been buried deep beneath Mars' quaking surface, and nearly all knowledge of it has been lost to time.

Walkthrough

A detailed walkthrough is available for this level.

Objectives

Shoot a hole in Mars

Get to the BFG-10000

Retrieve the power source

Evacuate the Phobos base

Reach the portal

Use the ion catapult

Get to the escape pod

Challenges

• Big Ba-da Boom - Kill 40 demons with a very big gun
• Disarmament - Destroy three arm cannon weak points on mancubi
• Lock and Key - Find the Slayer Key

Collectibles

Collectible	Count
Albums	2
Cheat codes	1
Codex pages	2
Empyrean key	1
Praetor suit points	5
Sentinel batteries	3
Sentinel crystals	1
Toys	3

Areas / screenshots

• 

  Ion catapult

• 

  The hole made in Mars by the BFG

• 

  The broken bridge leading to the slipgate.

Master Level

A Master Level version of this mission was released with Update 6.66 on October 26, 2021, which makes a number of changes to significantly increase the level's difficulty:

• The number and variety of monsters is greatly increased, including the whiplash spectre from The Ancient Gods, Part One. Monsters that normally appear later in the campaign are included, including tyrants and arch-viles.
• Collectibles, challenges, secret encounters and the Demonic Corruption meter are removed, along with the automap station and the Slayer Key. Some items are replaced with soulspheres or spirit armor.
• Environmental hazards such as laser grids, heavy fog and purple goo are added throughout the level.
• Ten challenges are introduced which require the player to complete the level at different difficulties, including Ultra-Nightmare. The "Classic Mode" introduced with the Super Gore Nest is retained here, where the player starts with an unmodified combat shotgun (plus all auxiliary weapons and the plasma rifle collected in the opening cutscene) and must collect more weapons and modifications as they progress. Each individual challenge has its own cosmetic item unlock, and completing all ten challenges unlocks a red chrome skin for the plasma rifle.

Pre-release

QuakeCon 2018

A shortened version of the first half of Mars Core was the second level of Doom Eternal to be displayed to the public in the QuakeCon 2018 reveal on August 10, 2018.

The noticeable differences from the reveal to the final product includes the following:

• The player takes control of the Slayer before walking into the elevator, as opposed to starting inside the elevator in the final version.
• The PA system inside the Phobos outpost has a different voice actor, as do the various UAC scientists and guards in the opening cutscene.
• The exclusion of the green cracks indicating a punchable object on a vent.
• The exclusion of the UAC Spokesperson hologram before exiting outside.
• The exclusion of an extra life outside.
• The exclusion of Samuel Hayden and VEGA throughout the level, presumably to avoid spoilers.
• The exclusion of the Doom hunter and dread knights near the BFG-10000.
• The exclusion of the chaingun throughout the level, likely being developed at that time. The final version introduces the chaingun as a mandatory pickup in Super Gore Nest to advance the level, although the part of the level itself was not seen at that time, further supporting the theory.
• The main entrance to the BFG-10000 is accessible in the reveal, which contains an arch-vile. The Slayer pulls out and swings his Crucible blade in a cinematic, after which the reveal ends. In the final version, however, the main entrance is inaccessible and a maintenance hatch underneath is taken instead. Both the arch-vile and the Crucible are introduced later, in Taras Nabad.

GDC 2019

In this footage of the level playing in Google Stadia there are the following differences:

• The demons' spawn particles are yellow.
• There is an extra life on the floating platform before reaching the tunnel with spinning debris.
• Dash pickups have a different model.
• There are no barons in the arena outside the large building after the large dash section. Among the fodder in that arena are shield soldiers and gargoyles which are not there in the final version.

E3 2019

At E3 2019 the last section of Mars Core was shown, the differences are:

• After landing on Mars there is no speech from Samuel Hayden or Codex entry about Hebeth.
• At the entrance to the last arena there is a plasma rifle with a microwave beam mod.
• At the end there is a small cutscene in which a tyrant comes out of the slipgate and aims its rocket launcher arm at Slayer, who in turn pulls out the BFG.

QuakeCon 2019

At the QuakeCon 2019 presentation there were two full live playthroughs of the demo version of the level. One was with Hugo Martin, the other was a speedrun race between ByteMe, BloodThunder, ZELLLOOO and KingDime, with commentaries by community manager Joshua Boyle. The differences between this and the final version are:

• UAC personnel and soldiers still have voice-overs from a previous presentation.
• After the intro cutscene while the level is loading there is a different description: "The Slayer has come to the UAC Orbital Base on Phobos to find a route to Mars, and stop all demons in his path..."
• After loading the level, the player begins in the room with crates prior to going outside. There is no baron here, unlike in a previous presentation and in the release.
• The room between the crate room and the airlock outside has one extra life instead of a rune.
• Demons still have glowing eyes.
• Inside the airlock is a heavy cannon with the precision bolt mod. After picking it up, a tutorial for its mod appears.
• There is no UAC Spokesperson anywhere.
• In the outside arena there are no gargoyles like in QuakeCon 2018, or cacodemons and mancubi like in the final version. In other respects it is similar to the enemy layout like in QuakeCon 2018 and release.
• The arena in front of the BFG-10000 is never reached, instead there is a portal to the floating platforms section with the loading screen description: "Mars has taken catastrophic damage, exposing the core of the planet. The Slayer must find a way to reach it..."
• On the last platform to the entrance of the UAC outpost is a super shotgun.
• At the end of the path to the right from the entrance to the UAC outpost is a rune. The extra life that is in this location in the final version is closer to the entrance. The rune cross automatically grants the equipment fiend rune instead of giving the player a choice.
• In the arena with two portals there is no buff totem, mancubus, or dread knight.
• In the secret that in the final version holds a praetor suit point and secret encounter, there is instead a "perk" called "Vacuum", corresponding to the final version's sentinel crystal bonus "Loot Magnet".
• The secret near the ion catapult contains an unspecified secret item and generic tutorial for secrets instead of playing a prowler toy animation like in the final version.
• The rune that is at the ion catapult in the final release is absent in this version.
• After the ion catapult cutscene there is a loading screen with the description: "After battling his way across broken planetary structures, the Slayer is now close to reaching the ancient core of Mars..."
• After the ion catapult cutscene, instead of in the hit building, player regains control close to the building that has the shuttle after a cutscene showing that building and a glimpse of a sentinel crystal (that automatically grants a health increase upgrade).
• Instead of a sentinel crystal in this outside area, there is another "perk" called "Flame - More Loot", corresponding to the sentinel crystal bonus "Belch Armor Boost".
• In the airlock entrance to the shuttle building there is a chaingun.
• After entering the slipgate in the final part of the level, there is a screen thanking the player for playing the game.

Inspiration and development

• According to Hugo Martin level ideas are born from the mission design script, and here, the Slayer would be told to go on a big journey to the center of Mars, but instead in his characteristic defiance of authority shoots his way directly through the surface of the planet. This is reflected in the final version of Mars Core, where Samuel Hayden in the cinematic prior to the start of the level tells the Slayer that "getting there will take time" and that "there is no easy way to access the core of Mars", and is opposed to the idea of the Slayer using the BFG-10000.

Trivia

• Development resources and developer-only portions of the level refer to the final Martian core area of the level as "Hell," and indeed, various infernal influences seem to be present in that location in the form of torrents of lava and other small objects which do not obey normal gravity, and a whispering voice that can be heard on the wind when the Slayer first lands his escape pod. The Fast Travel system also refers to this area as Hell, indicating that the nature of the curse on the area is demonic in origin and has lingered on since the fall of the city. The aforementioned whispering heard sounds similar to the voice that narrated the Slayer's Testaments in Doom (2016).
• Two of the Fast Travel destinations in the meteor section of the level are titled "Alpha Labs" and "Delta Labs". They may be a reference to the Doom 3 locations of the same names.
• In the Master Level version of this stage, two tyrants appear by the final slipgate. This may have been inspired by a reveal video at E3 2019, which ends with a tyrant emerging from that portal.
• According to creative director Hugo Martin, the otherwise redundant scene of obtaining a plasma rifle in this level was left in the game because it was "badass".
• If you use noclip and go through the door where the intro cutscene starts, you can teleport into the dev room, where you can pickup a BFG and teleport to different sections of the level thanks to the teleport pads.
• Via the console command trigger cinematic_cineractive_e2m3_core_supergun_entrance_archvile_intro_sync_2 you can hear the original voice-overs of the opening cutscene and also play the arch-vile's cutscene; after it ends the monster continues to stand in its position.

Bugs

Using the flame belch, and then pressing the button next to the ion catapult in quick succession so as to be almost simultaneous will make the event fail to trigger and put the player in a weaponless state. This necessitates a checkpoint reload.