Early on in Doom Eternal, the Doom Slayer visits the world of Argent D'nur, where futuristic tech is merged with a gothic, medieval aesthetic. There, the player will encounter frequent references to an order of fallen warriors known as Night Sentinels. While Doom Eternal's lore pages scattered throughout the levels will gradually reveal their history, it is easy to miss out on the full story, which sheds light on the Doom Slayer's past, as well as the machinations of the nefarious Kahn Maykr.

Despite the Doom franchise's simple initial premise—a lone marine on Mars kills demons with guns, chainsaws, and anything else that looks promising—the series' lore has evolved radically throughout it's history, and much of Eternal's lore occurs in Doom (2016)'s backstory. Prior to being excavated by Samuel Hayden, the Doom Slayer fought the tides of Hell alongside the power-armored warrior caste of the Argenta.

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Founded by the first King of the Argenta, Ormero the Father, the Night Sentinels were something akin to nobility in the warrior culture of Argent D'Nur, acting as the planet's peacekeepers and military. When Hell's forces first attempted to invade their world, the Sentinels were there to meet them in battle. And when the Doom Slayer was discovered, raving and incoherent with rage, he was permitted to stand trial by combat in the Argenta's coliseum, and ultimately welcomed into the ranks of the sentinels by King Novik, the order's current leader.

Custodians of the Wraiths

Argent D'Nur was host to alien entities known as the Wraiths, which gradually gave rise to all life on the planet, including the Argenta. The Argenta revered the Wraiths as gods, and the Sentinels were originally formed to protect them. In exchange, the Wraiths powered the Sentinels with their elemental energy, making them nearly invulnerable in battle, and powering their fierce armaments. The Order of Deag, the planet's priesthood, worked closely with the Sentinels and oversaw worship practices toward the Wraiths. When the race of eldritch aliens known as the Maykrs arrived, led by the Kahn Maykr, both the Sentinels and Order of Deag accepted them as their new rulers and overlords.

Why this proud warrior race adopted a second set of godlike alien overlords is never revealed, and doesn't really make sense, but then again, many things about Doom Eternal defy logic. Despite this, both parties continued to dedicate themselves to the protection and worship of the elemental wraiths, whose energy was the lynchpin of their society. The Maykrs also had a vested interest in the Wraiths, as their energy was one of the few power sources potent enough to help fuel the "transfiguration" ritual that perpetuates their existence. But the Wraith's energy was not sufficient in and of itself.

Civil War

When Hell attempted to invade Taras Nabad, the capital of Argent D'Nur, the Night Sentinels met them in battle and drove the invasion force off. And, when the Doom Slayer entered their ranks, he led a contingent of Sentinels deep into Hell's territories, cutting a bloody swathe through their legions. The Maykrs, however, were intrigued by the power fueling the demonic legions, known as Hell Essence. The Maykrs, and the priesthood of the Order Deag, began to experiment with this power, and discovered that by fusing Hell Essence with Wraith Essence, they could create the seemingly limitless power source known as Argent Energy.

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The Sentinels rejected this "elixir," and quickly came to discover how it was created: the Maykrs used lesser Argenta as slaves to produce Hell Essence via torture, which would then be merged with Wraith Essence and refined into Argent Energy. King Novik and his Sentinels rebelled against the Khan Maykr, while legions of other Argenta remained faithful to their alien masters. The Order of Deag appeared to stand with the Sentinels and King Novik, though in secret, they actually served the Khan Maykr who covertly joined forces with Hell.

The Betrayal and the Betrayer

The Order of Deag fed the Night Sentinels bad information, baiting the warriors deep into the bowels of Hell... and then sealed the portal behind them. The Sentinel who were cut down later became Marauders—Doom Eternal's most punishing enemies, and one can clearly see similarities between their armor and that of the Doom Slayer. Thanks to the Order of Deag's deception, all of the Night Sentinels were slaughtered or transformed into Marauders save for two: the Doom Slayer, and the Betrayer.

The Betrayer, formerly known as Valen, committed treason by providing Deag Grav access to the Wraiths, in exchange for the resurrection of his murdered son. With the Maykrs now possessing free access to Wraith energy, Hell's legions became utterly unstoppable, and laid siege to the kingdom Valen had sworn to protect. Worse yet, Deag Grav resurrected Valen's son as the Icon of Sin: a hellish titan with no remnant of his former humanity. In penance, Valen exiled himself into Hell, where the Doom Slayer encounters him in Doom Eternal.

Doom Eternal is available now for PC, PlayStation 4, PlayStation 5, Stadia, Switch, Xbox One, and Xbox Series X/S.

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