- "Speaking of that blacksmith, he also recovered plans for "The Agarthan Device". It seems that the blacksmith already built one of the pieces - the fabled "Vril Vessel". The Agarthan Device, a device capable of granting that which one desires... Almost like ein 'genie in a bottle'... Perhaps I will keep this genie in mein back pocket..."
- — Edward Richtofen, May 15th 1942
The Agarthan Device or Seal of Duality (lit. Lock of Duality in Keeper) was an artifact featured in the Aether Storyline of Zombies mode. In Call of Duty: Black Ops 4, the artifact is referenced in the maps Classified and Alpha Omega before being featured in Tag Der Toten as a quest item. It is capable of manifesting the will of the user into reality, as well as resolving the duality between Keepers and Apothicons (as indicated by both the Apothicon Blood and the artifact's inscription).
The Agarthan Device was sought by both the Keepers and the Apothicons as an artifact of ultimate power, however unlike the Summoning Key which was created at the beginning of time so the First One could seed the dimensions with life, the Agarthan Device didn't exist; as such, the two factions were forced to use humans in order to attempt to gather the components for the device.
- "The angels came down to Old Jeb and told him what to do. Build yourself a great machine, its punch will see it through. When you pack-a-punch, the whole damn bunch will not last very long. And while you put yourself to work, sing a country western song."
- — The Pack-a-Punch jingle, detailing Jeb's encounter with the "Angels"
The first known instance of this intervention occurred in 1885, when after initially instructing him to construct the Pack-A-Punch Machine, Jebediah Brown was given a secondary task of constructing the so-called "Agarthan Device", from its three components: The Blood of a colossal Apothicon (known as an Apothicon Elder God); an Elemental Shard, formed through permanently binding four souls to the Aether through a piece of Element 115; and a metallic vessel for them to reside in. As a result of the limited technology of the time. Brown was unable to recover the blood from the dormant Elder God at the bottom of the ocean, nor bind the souls of four individuals to a piece of 115 - however he was able to forge the metal vessel.
In the final act of constructing the vessel, Brown used the Pack-A-Punch machine to charge the component. The sheer energy emitted caused severe temporal rifts, lodging The Town of Purgatory Point underground in Angola, wherein the remaining townsfolk - Brown included - were killed by undead.
The vessel - dubbed the Vril Vessel by Edward Richtofen, and the schematics for the device proper were recovered by a Group 935 excavation in Angola, along with pieces of the original golden Pack-A-Punch Machine and Vril Device. Richtofen, in the process of devising his Grand Scheme viewed the Agarthan Device as a potential useful asset, should his plan fail. Using the Vessel, Richtofen was successful in binding the souls of his three test subjects (Tank Dempsey, Nikolai Belinski, and Takeo Masaki) along with his own soul, to a piece of 115, causing it to transform - becoming the Elemental Shard. A byproduct of this was that those four souls were now intrinsically bound to the Aether. After learning of Richtofen's research, and seeking to cause discord within the group, OSS spy Harvey Yena reported Richtofen's use of 935 funding for personal projects to Doctor Maxis, causing the Elemental Shard to be sent to the Japanese Division 9 for research, and Richtofen to be re-stationed at Der Riese. The Vessel, however, was never found as it was secured within a hidden safe in the walls of the Siberian Facility.
Years later, still undercover for the US, Harvey Yena would bring Richtofen's research into the Agarthan Device to The Ascension Group, under the false pretense of a decisive victory in the cold war for the Soviet Union. This renewed interest would result in the location of the Apothicon Elder God, with its blood being extracted by the Russian scientists aboard the Soviet Research Vessel known as the Tugarin. Eventually, however, their experimentation would cause the ship to crash on the shores of the Siberian Facility, with the blood killing the entire crew.
The Elemental Shard was eventually recovered from the Japanese by the United States after the second world war, where it was stored at Groom Lake until its acquisition by Broken Arrow. Cornelius Pernell - now Director of the organization - engaged in intensive research and study into the Shard, drawing suspicion from the Department of Defense. Concerned for National Security, the DoD attempted to seize the shard and send it to another Broken Arrow locale, away from Pernell; unbeknownst to them however, Pernell had split the shard in two, keeping one half for himself to continue his research. After his ascension and the immediate closure of Camp Edward, his half of the shard remained locked within the American Pyramid Device.
The second half of the Elemental Shard was studied by Broken Arrow scientists in order to create the Bios. Victis eventually use this half of the shard to power devices that allow them to reach The Empty Earth, with this fragment of the shard seemingly being consumed by the machine in the process.
Breaking The Cycle
After his acquisition of The Kronorium after the events of Blood of the Dead, Primis Nikolai learns of the Agarthan Device, and of its capability to finally break the cycle. As a result, he recovered the still-remaining half of the Shard from Camp Edward in Alpha Omega.
Due to the shared souls of Primis and Ultimis having been bound to the Aether through the Shard, Primis Nikolai, aided by Ultimis Richtofen, utilize Victis to recover the remaining components of the Agarthan Device from a pocket containing the Siberian Facility, with them being aided by the spirit of Pablo Marinus, trapped in a purgatory within.
Victis find and sate the Apothicon Blood, with it accepting that the "Duality must be resolved" and it giving itself willingly to the device, reunifying the Keepers and Apothicons within the Aether for the first time since before the War of Agartha. With the device almost complete, Victis begin charging it using the Pack-A-Punch machines located around the frozen tundra, eventually reaching Jebediah Brown's original and more powerful Golden variant. According to Nikolai, as the device is integrated with the entire Aether via the Elemental Shard, this final upgrade causes all 115 to begin rapidly and irreparably transforming, resulting in the ground becoming scorched.
Giving the finally completed device to Pablo, he utilizes its ability to send himself back to The Great War in order to inspire and save the life of Primis Richtofen, setting into motion the events that allow Blood of the Dead to successfully occur. After this, Victis send the device back to Nikolai, wherein he utilizes it's namesake (Lock of Duality) with the Summoning Key (or All Key in Apothicon) in order to open The Way Through - the path to a universe free of the various forms of corruption - for Samantha and Eddie, with all else being banished to the Dark Aether.
- "The Agarthan Device can do many things. It has the power to open and close new worlds."
- — Nikolai Belinski describing the Agarthan Device's abilities to Dempsey.
The Agarthan Device - much like the Summoning Key - has been seen to demonstrate multiple different abilities, all of exceptional power, to the point where it was desired by Humans, Apothicons, and Keepers alike. Its most notable function is the ability to "grant the bearer that which they desire", essentially granting any wish. This is demonstrated by Pablo Marinus, where he is able to instantaneously travel through time and space to arrive back at The Great War.
Secondly, as stated by Nikolai during Salvation Lies Above and demonstrated in the ending cutscene of Tag Der Toten, the device has the ability to "open and close" new worlds. This is seemingly only possible once used in tandem with the Summoning Key, as the names of both artifacts suggests a lock-and-key relationship.
Its tertiary function, as suggested by the Apothicon Blood, is to "resolve the duality" between the Apothicon and Keeper races, that has existed since the two became separate following the banishment of The Shadowman's faction after The War of Agartha. This function is furthermore implied by the Keeper inscription on the Seal of Duality, which reads "Mirhomolak Mirroc la Korgra" or "Hold Captive Light and Shadow".
The Agarthan Device appears as a golden vessel, somewhat similar in design to the Vril Device (likely as they were both crafted by Jebediah Brown), with a large centrall recess. This central area can open, allowing the placement of the other components required for the device to operate. The golden vessel is inscribed with the Keeper phrase "Mirhomolak Mirroc la Korgra" or "Hold Captive Light and Shadow".
- In Classified, a wall chalk shows the Vril Device alongside the Elemental Shard, under a diagram labelled "The Way Through", possibly implying that Treyarch were originally intending to use the Vril Device rather than the Vril Vessel.
- In game, the Apothicon Blood begins speaking in Keeper and says the Keeper translation of the Seal of Duality, however an error was made and "seal" was accidentally swapped out for "egg", a very similar word in Keeper.
- "“Leesanatahn lu ahm (Seal of Duality)… We speak now the tongue which is forbidden. Bring us the Seal of Duality… That we may cleave to our sworn enemy. We must restore that which was separated.” - Apothicon Blood
- "The Duality has been resolved... Arkeon (Start)... Kareon (End)... Asteon (Forever)" - Apothicon Blood