"No mercy to the Omnissiah's enemies, no pity for those who deny the Emperor, no respite for those who defy the might of Terra and Mars. They shall die hearing only the glories of the Machine God, unable to bear the power of His thunderous voice."
- —Excerpt of data fragment Phi-Omega-Nu-Omicron-Sigma
Far from the Well of Night, in what was once the ancient Jericho Sector's Zacchaeus' Expanse Sub-sector, lies a small, jungle-covered world that might otherwise have come to support a Human colony in its own right, but for the intervention of the Adeptus Mechanicus.
The world's original name is long lost to history, and it is now known only by a designation applied to it by the Explorators who rediscovered it, based on the few data fragments discovered about the world: Phonos.
The world's only known Human-made structures are at a single, isolated Adeptus Mechanicus facility, locked within a stasis field for what might have been thousands of Terran years.
However, Phonos itself was set upon by the Tyranids of Hive Fleet Dagon, and when the Imperium sent forces to investigate, they faced the full force of the Tyranid menace and paid dearly for it, losing most of Battlegroup Argo, including Lord General Mikal Curas, in the process.
Little is known of the history of Phonos, not even its true name, but what little exists has been pieced together from data-fragments and the initial reports of the Explorators.
At some point after the Horus Heresy, the Adeptus Mechanicus established a facility on an unclaimed world within the border territories of the Jericho Sector.
The facility remained operational, subject to the will of the Jericho Sector's highest-ranking magos as all Mechanicus fiefs within the sector once were, for several thousand years. During that time, it adhered to a mandate of secrecy and isolation, limiting contact with the rest of the galaxy.
Such a mandate is, typically, only employed by the Mechanicus to protect the most advanced and arcane of technology, such as archaeotech, rare configurations of a Titan combat walker, and other mighty war engines such as the unique and terrible Ordinatii.
As the Age of Shadow descended upon the ancient Jericho Sector, the isolated facility cut itself off further, with all communication with the rest of the sector ceasing by the end of the 35th Millennium. It is believed that, at this point, the facility activated a stasis field generator contained within its structure, sealing itself off entirely.
The last communication anyone received from the facility on the world now known as Phonos was a stream of unintelligible machine code, which forced its way between the minds of hundreds of astropaths, eventually stopping upon worlds containing datacrypts and archive repositories, cleansing them of any reference to the facility.
In the latter half of 812.M41, an Achilus Crusade expedition accompanied by a contingent of Adeptus Mechanicus Explorators reached Phonos. As soon as the first report of Phonos' discovery arrived at Watch Fortress Erioch, the Omega Vault opened another of its many doors.
Contained within the ancient, long-sealed chamber was a device, unrecognisable to all but the learned eyes of Watch Fortress Erioch's Masters of the Forge. The device appeared to be some form of control wand, apparently designed to interact with stasis field technology and believed to be linked to the facility on Phonos. Whether this is the case is yet to be seen, for nobody from the Deathwatch has yet managed to reach Phonos to employ the device and test the theory.
Little more than speculation exists about the facility and its contents, but the extensive nature of the security measures involved have led many amongst the Adeptus Mechanicus and the Inquisition to believe that the facility contains some form of extremely advanced weapon or war engine.
Given that other data-fragments tell of the "Omnissiah's voice" and "the killing noise," many who are privy to such secrets believe that the device may be some powerful form of Sonic Weapon, akin to an Ordinatus.
If this is the case, then so deadly an engine of war would be a valuable asset to the defence of the Orpheus Salient, and a terrible threat if it fell into the hands of a group such as the dark magi of Samech or the Stigmartus.
All that is known about Phonos for certain is that it is a world in the maw of the Great Devourer. When contact was lost with the Orpheus Salient, General Mikal Curas transferred his command to the Imperial Navy's Battlefleet Argo, and set out to Phonos to investigate. Three and a half solar weeks later, Battlegroup Argo arrived at the system's edge, to bear witness to a world being devoured.
The Tyranids responded swiftly to Battlegroup Argo's presence; a beast interrupted while feeding, it struck with inhuman savagery, pouncing upon Imperial Navy squadrons and tearing them asunder with blade-limbs, feeder tendrils, bio-plasma blasts and pyro-acid sprays.
Commanded by General Curas, Battlegroup Argo fought back valiantly, defiantly cutting apart the attacking bio-ships with salvo after salvo of continual fire.
For eleven straight solar hours of fighting Battlegroup Argo held off the Tyranid advance as best they could, but outnumbered fifteen-to-one, they could only survive for so long, slowly losing one ship after another.
The turning point came when the Mars-class Battlecruiser Cardinal Xian was boarded, its captain choosing to sacrifice the vessel by overloading her reactor rather than suffer the fate of death by Tyranid claws. With so powerful a vessel lost, the end was in sight for the battlegroup.
The first that was heard of the fate of Battlegroup Argo came six solar months later, when the first of the straggling picket ships arrived back in Imperial space, having borne witness to the destruction of the Orpheus Salient's most lauded battlegroup, and the death of its supreme commander.
The Nepenthe Imperative
The lack of available information on Phonos -- which is not the world's original given name, but rather an extrapolation from a single archive fragment amongst those discovered by Adeptus Mechanicus data-historians cataloguing ancient Martian Librarium Vaults -- is problematic to Explorators.
Only a few other details could be found within those fragments, including the location of the world, and references to an ancient Adeptus Mechanicus protocol referred to as the "Nepenthe Imperative."
According to what little information could be recovered on the subject, the Nepenthe Imperative is a meme-virus designed to spread to archives containing the targeted data, in order to prevent something being discovered. Many magi consider the Nepenthe Imperative to be a myth.
The Secret of Phonos
An Adeptus Mechanicus research facility was discovered on Phonos in 7628.812.M41 by the Explorator vessel Mathemantic Insight, and it is this facility which is believed to contain whatever the Nepenthe Imperative was initiated to conceal.
The facility itself is locked within a powerful and remarkably stable stasis field, which the Explorator mission was incapable of deactivating, leaving the facility as yet unexplored.
As yet, they have been unable to reach any clear consensus as to what may be hidden there, though one clue does stand out above all others: in the Adeptus Mechanicus' vast array of cipherdialects and code-languages, the word "Phonos" takes one of two meanings, depending on context and emphasis: "sound," or "murder."
The fact that the archive fragments that gave this world its current name provide no clue as to context or intended meaning, suggests that either or both meanings may tell of what lies within the stasis field.
Many of the following locations may have been ravaged and changed beyond recognition by the onslaught of the Tyranids.
Untouched by time for six thousand Terran years, the facility is enclosed within a stasis field, the structures within having remained exactly as they were the moment the field was activated.
From the outside, the facility appears to be a standardised design from the Adeptus Mechanicus STC canon, a Voss Pattern modular structure. Based on that and the observable configuration, certain details about the facility's structure can be ascertained.
The surface elements of the facility are a latticework of chambers and corridors covering approximately a square kilometre, equipped with Servitor-slaved defensive weaponry and landing facilities capable of supporting bulk cargo lifters.
Given the nature of this facility, it is likely that it extends deep underground, providing storage areas and more extensive shrines and laboratories than those found on the surface.
Due to the presence of the stasis field, a closer and more thorough examination of the facility and its layout cannot be performed. However, the field has also prevented the Tyranids from approaching the facility, in spite of frequent attempts.
Soon after the initial landing in 7628.812.M41, the Mechanicus expeditionary force began establishing outposts for a garrison force, intending to expand upon them when reinforcements arrived.
Table Mountain, a kilometre-high plateau in the midst of the broad valley north of Facility Phi-Omega-Nu-Omicron-Sigma, was selected to be the primary firebase, given its height and location, to provide anti-aircraft and surface-to-orbit fire against enemies attempting to land near the facility.
In 8040.813.M41, Phonos came under attack, having lost contact with the rest of the Orpheus Salient a little over two solar weeks before. Bastions and firebases established across Phonos were overrun swiftly by a living sea of insatiable monsters, and crushed beneath the claws and hooves of countless millions of soulless predators. Within a week, all that remained was the Table Mountain compound, surrounded on all sides.
The Astra Militarum garrison -- composed primarily of Guardsmen from the Gang Magna 632nd Regiment -- held their ground, forcing back the Tyranids with disciplined, well-directed fire repeatedly over the four solar days that followed.
The defenders relied on the high ground and reinforced fortifications of their position to hold off the land-bound creatures, while the anti-air guns and defence laser destroyed Gargoyles and other airborne bioforms.
The defence ended with the arrival of burrowing creatures, tearing upwards through the flat-topped mountain and bypassing the defences, slaying the Guardsmen.
The last reports of the Guardsmen on the ground were recorded and transmitted to Battlegroup Argo when it arrived at system's edge, the final words of Phonos' garrison carried back to the Imperium on a damaged picket ship.
It is extremely unlikely that any trace of the compound remains intact; indeed, if the world has not already been consumed by the Tyranids, then it is currently being devoured.
- Deathwatch: The Jericho Reach (RPG), pp. 124-125