Sentinel Prime

Sentinel Prime is an eponymous city on the homeworld of the Night Sentinels and their greater species, referred to as the Argenta, and is a location and the eighth level in Doom Eternal. The final of the three Hell priests, Deag Grav, is found here. However, in order to kill him, the gladiator has to be fought as a boss beforehand.

"You've traveled through the core of Mars, arriving at the ancient city of Sentinel Prime. You have Sovereignty in this unholy place...for now. The great Slayer was once a warrior king in this world - tradition grants you safe passage but the completion of your mission will come at a price. Hell Priest Grav is waiting."

- Loading description

Lore
This level features a couple of flashbacks set an indeterminate amount of time after the events of The Lost Levels which detail the Doom Slayer's arrival in the Sentinels' world. Most of the Codex entries of this level are backstory for the Argenta civilization, detailing their first contact with the forces of Hell and the events leading to the addition of the Slayer to their military ranks.

Upon arriving in the present at Sentinel Prime, the Slayer is greeted by a cathedral hall filled with Night Sentinels on either side. The Sentinels stand to attention, uttering the Slayer's war cry, "Rip and Tear!". A Maykr angel waits at the far end of the hall, welcoming the Slayer home. A Sentinel gives a command to notify Deag Grav of the Slayer's arrival before allowing him passage. The Slayer heads towards the gladiatorial arena. On his way there, a flashback from his point of view is shown, where he appears battered and beaten, being dragged towards the priests Deag Nilox and Deag Ranak. The Sentinels who found him inform the priests that he was discovered outside the city walls. One Sentinel steps forward and hands Deag Ranak Doomguy's (as he is identified by the game's subtitles) helmet. Doomguy begins to mutter the words "guts, huge guts" and "must kill them all". The priests, impressed by his tenacity and resilience, send him to the arena where he will receive his judgement through trial by combat.

After the flashback, the Khan Maykr appears before the Slayer in holographic form, offering him a truce, and later on offering to return to him "what demons took away from him long ago", if only he turns back and lets the priest live. The Slayer refuses, despite the Khan's attempts to persuade him otherwise.

Upon entering a lift, the Slayer is raised into the arena. Etched into the walls of the lift is a diorama (known as The Gift of Argent) depicting the Khan Maykr exchanging Argent energy with King Novik and the Argenta. Another flashback is triggered, showing Doomguy fighting in the arena. He knocks an opponent to the ground before shouting his war cry. The priest Deag Grav approaches him, commending his valor and believes the Doomguy will do well in combat, as part of the front line battalion. Doomguy once again speaks in a breathless and paranoia driven monologue about the forces of Hell and how he must kill them all. It is at this point that the Khan Maykr, whose curiosity had been piqued by the mention of these new adversaries, commands Deag Grav to bring the Doomguy to her for questioning.

The flashback ends, and Deag Grav is standing in the arena. The priest tells the Slayer that if he is killed on the sacred coliseum grounds, the Slayer will lose all sovereignty given to him by the Sentinels. Grav recites a spell ("Calommus V Turna") before disappearing. The gladiator emerges from a gate and steps into the arena with a thunderous roar. The beast slams its /flail onto the ground before attacking the Slayer. The Slayer is able to successfully stun the gladiator, and uses his Doomblade to destroy its shield. The shield shouts "Kar en tuk!" ("Rip and Tear!" in the Argenta language) before exploding. After this, the gladiator pulls out a second weapon and dual wields them, but this proves futile as the Slayer shreds the gladiator and uses its own weapon to crush its head. Deag Grav appears again, ensuring the Slayer that Earth will be consumed regardless of what happens to him. His head is blown off by the Slayer before he can finish speaking. The arena turns to a crimson red and Night Sentinels pour out from the exits and begin approaching the Slayer with their spears drawn. VEGA opens a slipgate and urges the Slayer to leave, with the Slayer tossing the token he gained from killing the Gladiator onto Deag Grav's remains before entering the portal.

Objectives

 * Eliminate Deag Grav
 * Kill the priest's guardian

Essentials
This level features no combat, except for the boss battle with the gladiator and the other demons it summons. Follow the walkway until you go through a door, then use the skull switch in the middle of the room to ride an elevator downwards and trigger a cutscene; after the cutscene, head straight forward through a circular room and walk past a hologram of the Khan Maykr to a room with forges. Continue through a door and follow the passage past another hologram, enter the next room and climb up the tall steps to a walkway, then turn right and head into a room with a large staircase where a third hologram will appear. Go up these stairs and head straight forward to a walkway leading to another elevator, then use the skull switch to find a fourth hologram. Continue on to a prison block and head straight forward to a portcullis guarded by two Sentinels, who will permit you to ride up to the gladiator's arena.

The gladiator is a baron-like opponent carrying a morning star/flail in his right hand and a shield in his left hand; the morning star is on a chain, giving it a deceptively long range. When the shield's eyes flash green, the gladiator will lunge at you with the morning star and create an opening for you to attack; he can also fire an energy wave at you, signified by the gladiator pounding the front of the shield using the morning star. Hitting the gladiator with enough force may stagger it, allowing you to perform extra damage with a glory kill; do not approach the gladiator unless he is staggered, or he will create a shockwave around himself by pounding the shield on the ground. Once the gladiator's health is depleted, use a glory kill on it to destroy the shield.

In the second part of the fight, the gladiator will replace the shield with a second morning star, allowing it to become more aggressive and increasing its variety of attacks - however, it is now more vulnerable to damage. If the gladiator starts twirling one of the morning stars, it will deflect any frontal attacks so refrain from attacking at this time. The gladiator has a special attack where it will launch the flails and trap you between two walls, before releasing ribbons of energy that must be walked under or jumped over - once the attack finishes the gladiator will launch itself at you. As before, watch for the gladiator's eye flashing green as you may be able to stagger it with a well-timed attack. Once the gladiator's health is depleted, finish it off with a glory kill to end the level. You will receive ten weapon points and an upgrade to the blood punch, allowing it to instantly charge when you glory kill a heavy demon.

Challenges
There are no challenges in this level.

Special items
As soon as you enter the room with the third Khan Maykr hologram, turn right to find the automap station.


 * Two extra lives
 * From the "History of the Sentinels - Part VII" Codex page, turn right to see a skull switch just below you. Press the switch then turn right and jump across to the opening in the opposite wall to find a 1UP.
 * After finding the Praetor suit point, turn right to find a 1UP.

Collectibles

 * One Praetor suit point
 * Climb up the stairs where the third hologram appears and turn right at the top, then follow the narrow passage round until you see a Night Sentinel spirit ahead that you can jump to.
 * Nine Codex pages
 * "Sentinel Prime" - on the starting walkway, just before the first door.
 * "History of the Sentinels - Part IV" - in front of you after riding the first elevator down.
 * "History of the Sentinels - Part V" - just after the first hologram of the Khan Maykr.
 * "History of the Sentinels - Part VI" - after passing the second hologram, enter the next room to find this page behind a metal barrier
 * "History of the Sentinels - Part VII" - from the previous page, climb to the top of the room and turn left at the walkway to find this page.
 * "History of the Sentinels - Part VIII" - behind the stairs where the third hologram appears.
 * "History of the Sentinels - Part IX" - near the second elevator.
 * "Deag Grav" - after riding the second elevator up, turn round to find this page.
 * "Gladiator" - in the final room before the gladiator's arena.

Pre-release
Some early screenshots of Sentinel Prime showed Mars in the planet's sky, possibly indicating that it existed on Phobos or Deimos in an alternate dimension or within a different time frame. This detail seems to have been redacted in the final game and replaced by a red-colored moon, which can be seen more clearly on the game's title screen when the player's current campaign is saved on this level.