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."

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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 Doom Slayer to their military ranks.

Upon arriving in the present at Sentinel Prime, the Doom 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 Night Sentinel gives a command to notify Deag Grav of the Slayer's arrival before allowing him passage. The Doom 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 Night 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 Doom 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 Doom 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 Doom Slayer will lose all sovereignty given to him by the Sentinels. Deag 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 mace onto the ground before attacking the Slayer. The Doom 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 mace and dual wields them, but this proves futile as the Slayer shreds the Gladiator and uses its own mace to crush its head. Deag Grav appears again, ensuring the Doom 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 Doom 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.

Challenges
There are no challenges for this level.

Special Items

 * 2 extra lives
 * After the Khan Maykr tries negotiating with the Doom Slayer about bringing back "what the demons took from him", there is a room with an overhead bridge, where one Codex entry can be found ("History of the Sentinels - Part VII"). Following the hallway all the way to the end, there is a skull switch that will allow access to the extra life.
 * In the room with the Automap, going up the stairs and turning right and following the hallway until the end, where a Praetor token can be found.

Collectibles

 * Automap
 * In the room with the stairs, where the Khan Maykr tells the Doom Slayer she has a world to save.


 * 9 Codex pages
 * "Sentinel Prime" in the starting bridge.
 * "History of the Sentinels - Part IV" after the elevator flashback.
 * "History of the Sentinels - Part V" after the Khan Maykr offers a truce.
 * "History of the Sentinels - Part VI" in the ground level of the room following the Khan Maykr's offer to bring back "what the demons took from him" if the Doom Slayer lets Deag Grav live.
 * "History of the Sentinels - Part VII" in the upper level of the aforementioned room.
 * "History of the Sentinels - Part VIII" in the Automap room.
 * "History of the Sentinels - Part IX" right after the Automap room.
 * "Deag Grav" in the cliff at the entrance of the arena building.
 * "Gladiator" right before ascending into the arena.
 * 1 Praetor token
 * In the upper floor of the Automap room.

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.