I wonder what sort of abilities you might see in a Starmetal Warstrider. I'm imagining some decadent First Age Solar building this obscenely expensive thing, getting stabbed extra hard by salty Sidereals because of it, only for the hangar to be lost for ages until the story happens upon it.
My approach would be for the Warstrider to have been made as part of a larger project, with direct Sidereal assistance, as another one among many contingencies and just-in-case measures. The Indomitable Stellar Emissary. Its intent was to serve as an emergency stand-in should the Loom suffer catastrophic damage; when piloted by a Circle of Sidereals, one from each caste, it would draw in their anima and refract it through the starmetal of its superstructure, forcibly reimposing the order of Fate and suppressing any force or being Outside it for one thousand
li in every direction. The obvious consequences for demons and various synthetic spirits placed Outside Fate by their makers were deemed acceptable in exchange for absolute surety that within the Emissary's sphere of influence, anything short of a faux-Incarna would swiftly wither and die along with whatever Wyld Sorceries it may have tried to insinuate into the world's fabric.
Naturally, the Warstrider was seized and weaponized during the Usurpation, allowing the Sidereal Host to destabilize the post-deific servants and Creation-defying Workings which had become commonplace in the Deliberative, giving other assets a crucial advantage in their own missions. It proved far too obvious a target to come through unscathed; the Emissary became increasingly battered as it was Sorcerously shunted from AO to AO, and its masters had no time to spare for repairs or even a full diagnostic intake of the machine. They had too much to lose by holding it back, and its pilots were the youngest, weakest members of the Fivescore Fellowship, chosen for this duty because
this was the most useful purpose they could possibly be put to. When its internal conduction mandalas cracked under the hammer-blow of a furious Dawn, it was decided to provide only the absolute minimum maintenance to delay catastrophic failure. When one of its legs was reduced to a twisted length of crushed, warped starmetal, the Sidereal Host simply assigned a handful of behemothic auxiliaries to help guard it in the field (after all, its prime value was derived from its presence alone, and thus its tactical capacity was of secondary importance.)
When a crucial stabilizing engram set finally melted under the strain of refining its pilots' anima, removing the protective filtering which prevented its aura from indiscriminately calcifying
everything around it, the Sidereal Host replaced the previous guard detachment and issued due notification to operatives within its AO. After all, they had all made their choice long before this: to raze the world to its foundation rather than allow the Deliberative to destroy it entirely. What was another irreplaceable wonder cast into the flames? If it offered even the slightest advantage to their cause, increased the odds of a decisive victory by even the slightest margin, then any sacrifice was not merely justifiable, but
essential.
By some stroke of fortune, the great machine survived past the Usurpation, although as a pitiable shadow of its former self. Repairs continued across the breadth of the Shogunate era, and by the time of the Twin Calamities, it was mission-capable once more. The oligarchs of Yu Shan promptly "requested" that the Warstrider be placed at the center of their realm, where it could be used to supplement existing quarantine and sterilization efforts against the Contagion - and later, as a crucial strategic defense against the possibility of the Crusade pouring through the gates of Heaven itself. It was difficult to find five Sidereals willing to man it and lend their backing to the oligarchs, but not impossible.
During the Contagion, it was an infuriating but tolerable inconvenience. Their own plan to resolve the crisis already involved the Maidens themselves; in that light, the Warstrider had value only as a potential additional layer of redundancy in the Loom-stabilizing infrastructure being assembled to assist in regulating Fate while its five prime administrators were away.
By the time of the Crusade, only a single junior member of the original Fellowship remained alive, and he was far too busy finding the recipients of the other ninety-nine Sidereal Exaltations, contacting them, bringing them to Heaven for training in the bare essentials, sending them out again to assist in the defense of Creation, and then repeating the process with their successors.
The Indomitable Stellar Emissary was eventually returned to the Forbidding Ivy Manse, and Chejop Kejak then moved it once more into a Deliberative-era storage vault in Creation to put it out of the oligarchs' easy reach. There it lies: scarred and battered, but unbowed. While its full power only manifests when crewed by a Sidereal Exalt of each caste, it is still a Warstrider built for the speculated challenges of a threat to the Solar Deliberative, and sufficiently clever occultists could find ways of eking out a respectable portion of its potential through massive reservoirs of stellar Essence, pilots who have cultivated using the Essence of the Maidens or of Fate, or even the binding of certain gods or elementals into its frame, seeking to buttress its innate energies with the Five Elements of Creation which naturally complement the Loom.
A full Circle of Dragonbloods, for example, could do quite nicely as the centerpieces of such a scheme, each contributing their anima as pilots to power its secondary and tertiary systems before infusing it further with fivefold stellar Essence, which could then be spared exclusively for use by its active components...
