Though an inconceivable distance to the average human mind, the stars were dangerously close in stellar terms. The system's four planets suffered insanely erratic orbits and were tormented by conflicting solar winds. This type of star system was common in the galaxy, but it was rare to find habitable worlds there, or planets at all. Worlds around such stars were catapulted into space during their formation, or torn apart before they were born. Those that did survive were inevitably rad-blasted into sterility.

Trisolian was no fit place for a human being, but the conditions that made Trisolian dangerous to human life made it useful to humanity. An unusual combination of gravitational flux and aggressive solar winds turned the four worlds into cosmic forges. Their atmospheres were rich with exotic heavy elements and precious isotopes.

It was the Heptaligon's purpose to coordinate the harvest of these things.

Each of the four planets had their own city-sized orbital mining platforms, but the Heptaligon was the largest of them, comprising seven stations anchored by tether-tubes driven right the way through the icy heart of Etrian's lonely moonlet, Momus. The interior of Momus had been hollowed out, and was also inhabited. Between the tube-tethers, long strings of macro-cabling tied the stations together in a complex web, suspending subsidiary platforms between the main, and allowing transit between all points on a bewildering number of routes. Although involved in resource acquisition itself, the Heptaligon's main purpose was to act as the processing hub for all elements harvested from the system. In Momus' frigid centre, various gaseous compounds were compressed into ingots of bizarre metals, then shipped up the tether-tubes to station Prima for out-system export.

As the Heptaligon was the nearest thing Trisolian could boast to a civilised world, it hosted the capital, its military command, organs of governance and so forth. This was no different to thousands of other similar outposts all over human space, and under normal circumstances Trisolian would have remained a backwater, had it not been for the major warp conduit that passed through the system on the way to the strategically vital nexus system of Beta-Garmon.

Trisolian was Mechanicum. There had been overtures from the Imperium that the operations be turned over to Terran control, but the Martian Synod, unwilling to relinquish a potentially vital strategic asset, had dithered and procrastinated for years, all the while apportioning other roles to the Trisolian cities to increase their importance until, finally, Trisolian four had collectively been designated as a forge world, with all the rights and responsibilities thereof.

Trisolian's position made it politically important. So the Trisolian System remained Martian, whatever that meant in those uncertain times.