The leading force on Sethis Major and its environs, the AdMech use the planet as a source of cheap energy due to the rich well of heat close to the surface. They operate large manufacturoms at the base which produce heavy military machinery, including large tank parts for the older Rhino and Leman Russ pattern tanks and parts for the imperial navy, which hopes to set up firmer routes there and a better voidport.
Their goal is to turn the planet into a fully operational Forge World but it is a lofty ambition which will take many generations, though this is little dissuasive to the priests of the cult of a Mars. Day after day, year after year, the manufactorums funnel heat from the vast oceans of lava up their specially devised Thermal Web, an ingenious matrix of wires that reach into the most important important sectors of Omin, feeding not only protection from the prodigious cold outside, but also the bulk of the power generated required by the industrial activity of the city.
The AdMech are, more than any other group, responsible for the survival of Omin and are not shy to pull rank on any who interfere with their activities. For less well-to-do citizens of the hive, crossing the AdMech through illegal heat taps that syphon energy from the web is a way of life and death.
The Tech-Priests themselves are a varied lot on Sethis Major. Some are freshly minted from the scholae on Macharia, sent to prove themselves in the harsh frontier of the Imperium's edge. Others are ancient, their flesh long since replaced by blessed steel and sacred cogitators, their memories stretching back to when Omin was little more than a mining outpost. They speak in binharic cant when among themselves, a staccato rhythm of clicks and hums that sets the uninitiated on edge.
The lower ranks of the Mechanicus—the servitors, the menials, the tech-thralls—form the backbone of their operation. Servitors shamble through the manufactorums in endless shifts, their lobotomised minds perfect for the repetitive work of assembly and maintenance. Tech-thralls, often criminals who've sold their freedom for food or heat, are barely better off, fitted with neural shunts that ensure obedience and augmented with crude bionics to survive the hostile work conditions.
Pavimentum Manufactorum (Stratum I-II) — The largest of the Mechanicus facilities, Pavimentum sprawls across twelve square kilometres of industrial hellscape. Its forges never sleep, belching toxic fumes and molten slag into carefully regulated disposal channels. Here, the heaviest armour plates are stamped and blessed, each one inscribed with micro-litanies of protection. The Manufactorum is overseen by Magos Dominus Xerxes-7, a particularly zealous adherent of the Cult Mechanicus who insists on personally blessing every hundredth tank tread that leaves the assembly line.
Synthfarm (Stratum I) — An oft-overlooked but vital installation, the Synthfarm produces the nutrient paste that feeds much of Omin's population. Vats of synthesised proteins bubble and ferment under the watchful gaze of lesser tech-priests, their work considered menial by their superiors but absolutely critical to the hive's survival. The paste tastes of absolutely nothing, which is considered a feature rather than a bug. Recently, the Synthfarm has begun experimental production of reclaimed biomass, though few outside the Mechanicus know what that means and fewer still want to find out.
Munitorum (Stratum II) — The armoury and logistics hub of the AdMech's military might. Rows upon rows of standardised weaponry sit in climate-controlled storage, from simple lasguns to the more exotic plasma weapons favoured by the Skitarii. The Munitorum is also where the Mechanicus stores their most precious resource: spare parts. In a place as remote as Sethis Major, a replacement servo-skull motivator or plasma coil might mean the difference between life and death. Accordingly, the Munitorum is one of the most heavily guarded locations in all of Omin.
Magos Dominus Xerxes-7 — The de facto leader of the Mechanicus presence on Sethis Major, Xerxes-7 is an imposing figure: three metres tall with six arms, half his head replaced by an intricate lattice of cogitators, and a voice that sounds like grinding metal. He arrived on Sethis Major eighty-three years ago as a junior Enginseer and has since risen through the ranks through a combination of brilliance, ruthlessness, and an almost fanatical devotion to the Omnissiah. He sees the Forge World project as his life's work—or what passes for life in his heavily augmented state.
Tech-Priestess Kappa-Nine — Overseer of the Thermal Web, Kappa-Nine is responsible for keeping Omin alive. She is younger than most senior Tech-Priests, having been elevated to her position after solving a critical failure in the Web's secondary heat exchanger matrix that would have frozen an entire hab-block. She is less augmented than her peers, retaining much of her original face, which some whisper makes her too human. She doesn't care—she has the Web to maintain.
Lexmechanic Orpheus Vand — A disgraced Lexmechanic from the forges of Stygies VIII, Vand was exiled to Sethis Major after an "incident" involving forbidden archaeotech. He now serves as the keeper of the Manufactorum's data-vaults, endlessly cataloguing production quotas and machine-spirit temperaments. Despite his fall from grace, his mind remains sharp as a monomolecular blade, and he knows more about the history of Omin's manufactorums than anyone living.
Skitarii Alpha Primus Designation: Rho-12 — Commander of the Mechanicus's military forces on Sethis Major, Rho-12 is more machine than man. His tactical acumen is without question, his loyalty to the Omnissiah absolute. He and his Skitarii rangers patrol the perimeter of Mechanicus installations with ruthless efficiency, and they've been known to gun down heat-tap thieves without warning or mercy. The citizens of Omin fear the rust-red robes of his cohort almost as much as they fear the Black Ships.
For the AdMin, Omin has proven an unruly ground for the faith. They are far away from a shrine world and sincerely lacking in the usual resources to bully and indoctrinate the Imperial Creed. They have managed to get a large cathedral to Macharius built in one of the high places of Omin but some say this was a consolation prize so that they'd leave Omin alone for a bit longer. Their militant arm, the Sisters of Battle of the Order of the Charred Veil, have no presence on Sethis Major and so the Adeptus Ministorum must look to their most devoted vigilantes and priests to bring the Emperor's Light to the people of Omin.