The Slayer arrives in a new brand new realm for him to slaughter and conquer, this time his vicctims being a Lovecraftian inspired eldritch horror realm, with beings beyond our understanding, massive shadows of entities, tentacles being present everywhere.
"
The Cosmic Realm is a dimension of unfathomable dread where reality warps and sanity falters. Ancient structures of impossible geometry rise from the blackened seas, their surfaces pulsating with unholy runes. The skies churn with colors unknown, inhabited by titanic beings that defy comprehension. The Oracles of Argent, seers and keepers of forbidden knowledge, whisper of a theory: that the Wraiths, Argent D'Nur ancient gods, may trace their origins to this very realm."
First thing that happens in the realm is him obliterating whatever entities that are present there, until we see just a puddle of blood and meat remain.
Grabs an eldritch weapon from the Cosmic realm called the dreadmace, which is the most powerful melee weapon in the game, and the second most powerful melee weapon in the entire DOOM franchise, it's stated to be infinitely dense, and he wields it with a single hand absolutely effortlessly.
"Amongst the scholars of Argent D’Nur the Dreadmace stands as a weapon cloaked in mystery and dread. Its origin and material composition remain unknown, alien to anything the Sentinels have encountered before. It is infinitely dense and roiling with energy beneath its surface. Its mere presence distorts the mind, rendering Sentinel scientists and engineers incapable of conducting thorough examinations."
"Our covenant with the dark realm is sealed" "Now their strength is our own" the Cosmic realm now has the power of Hell fused into them, and their beings.
https://youtu.be/TlbtituG6Oc?t=13
The Cosmic Baron, being one of it's mightiest beings, Slayer instantly faces it in close combat with "Into The Void" ramping up in the background just to farm more aura with metal, reducing it into mush literally within seconds of it facing the slayer. as to where he keeps it down, by stepping on it and rips it's head in half with his shield,
Just listen to the first minute of the theme and you'll know enough, it's fire.
"The Cosmic Baron, a construct of eldritch design, emerges from the mollusk vats of the Okkryth Synthesists, techno-sorcerers of the Cosmic Realm. Forged through gene splicing , its grotesque form mirrors the Barons of Hell and marks the unholy union between their worlds."
Faces an army of demons, and pulverizes a mancubus with the dreadmace.
Gets swallowed by The Old One, instantly starts to fight throughout it's innards, which is large enough to house entire arena's
Grabs an acolyte by the neck while ripping it's heart out.
"
Once hallowed sentinel priests of Argent D'Nur, now vessels of cosmic corruption. Their souls twisted by the
Witch's eldritch touch, these fallen oracles peer beyond mortal veil with mind poisoned by alien essences.
The Cosmic taint courses through their veins, bestowing forbidden sight and powers that rend the fabric of reality. They serve as one - a serpent with many heads, each a fragment of their mistress's unfathomable design. Through them, the malice of realms beyond bleeds into the world they once swore to protect."
Rampages through the body of the Old One, destroying the veins to it's heart, until he finally blows it's heart up from the inside with the BFC.
The Old Ones corpse lies behind the Slayer as he moves on with his objective.
Perfect example of the power from the dreadmace, completely destroys the body of an Agaddon Hunter with a single hit.
His heavy ass footsteps are literally always audible through the ENTIRETY of the game, just to let you know that he's a literal walking tank.
Purely for the sake of badassery.
Thyra is infront of him, which is why he went into the Cosmic realm in the first place, but the Demons attempt to stop him from reaching her although futile.
Hundreds of demons along the way, including elite and superheavy demons.
Obliterates a pack with a single shot of the chainshot cosmic weapon.
"
The Chainshot is a terrifying artifact, pulsating with a sentient malevolence that whispers from the abyss. Born from the unfathomable depths of forgotten realms, it channels chaotic energies, hurling its projectiles with a force that tears reality itself. Its origins are veiled in ancient lore, rumored to be crafted by deities who once held dominion over the stars. The weapon crackles with azure lightning, each shot imbued with a sinister malice. Only the strongest of wills can withstand its insidious whispers, which gnaw at the edges of the wielder’s sanity."
the weapon itself is powerful enough to tear reality itself, although the Slayer is completely unaffected by any side effects whatsover, such as gnawing at the wilder's insanity.
Doomslayer attempts to rescure Thyra, but the Wraiths (Gods of the Cosmic realm) within her attack the slayer and seem to incapacitate him for a while, which causes Ahzrak to show up,
Ahzrak explains that she has an ancient sentinel god within her.
Kreed says Ahzrak should kill the Slayer, with Ahzrak replying that they need "
something more permanent" implying they can't truly kill the Slayer.