Your ARACHNE//WARCHIVE comes online, whole libraries of military simulations accessible to you, some of them impossibly unrealistic or antiquarian, playing as strange Imperial bio-machines fighting against primitive sublight combatants, trading fusion warheads and mass driver pellets.
Since we're at a point where we've developed enough that this is basically guaranteed to be in-character knowledge thanks to Arachne's internal industrial capabilities and newfound military knowledge, let's talk about
Invariant Technology. Invariant Technology is the phrase used to delineate technology which is not dependent on metric-alteration and spatial-programming -mature molecular nanotechnology and fusion technology. Invariant technology not only needs no Architecture to construct, it needs no Architecture to maintain. Invariant Technology precedes the Empire, its origins lost to deep time, and has been mature and unchanging for eons. The sole difference between Invariant Technology at the Empire's zenith and the Invariant Technology preceding it is that the Empire makes more extensive use of rare elements and antimatter, as Architecture permitted trivial antimatter generation and atomic alchemy.
Invariant technology engines and power systems generally were fusion-based, although some invariant technology uses antimatter when high power storage is necessary. Invariant weapons systems include chemical-, fusion-, or antimatter- engine guided missiles, electromagnetic launchers, and directed-energy beam weaponry, similar to ironcasters and beamers. Projectile munitions built with invariant technology generally use antimatter-catalyzed fusion warheads. Invariant shielding technology generally made use of composite armor materials with monocrystalline or amorphous metals combined with carbon-fullerene or carbon-nanotube weave, which was incapable of protecting from direct hits from fusion-warhead munitions but provided otherwise excellent resistance to kinetic- and directed- energy weapons and near-misses from fusion warheads. Invariant biotechnologies allow for biological immortality, consciousness backup and upload, radical human augmentation (including intelligence augmentation), and the creation of synthetic life.
Although impressive, these technologies are no match for exotic equivalents. An invariant antimatter drive can accelerate a missile at hundreds of gravities. Meanwhile, a FORCE voidcruiser's warp drive is capable of near-arbitrary acceleration and deceleration under subluminal flight regimes, while also providing an additional protective layer and the option to engage in short-range superluminal (faster than light) travel. An invariant supercomputer can solve extremely difficult problems and process enormous amounts of data. An exotic tactical computer may permit negative reaction times thanks to acausal channels and can engage in hypercomputation. An invariant missile can accelerate to several percent of the speed of light while carrying multiple megaton-range fusion warheads, each capable of destroying a metropolis - but a FORCE drone can suppress nuclear fusion with its countermeasures suite, has mirrorfields that can deflect arbitrary amounts of incoming energy, and phaseskin which permits it to allow the missile or its explosion to harmlessly pass through the drone. Although you could theoretically use invariant weapons to harm an Empire war machine, doing so requires extensive information warfare use to mitigate enemy countermeasures - and even then, the defensive fields and exotic strong-force and unified-force bonds that make up the hull-armoring of an Empire drone or voidcruiser together are far tougher than any matter, and can survive even these artificial stars.
Because exotic technology was overkill for the creation of everyday items while molecular and atomic manipulation was trivial, most citizens in the Empire would spend their lives surrounded by invariant technology, which was cheaply and easily available to citizens of the Empire. Emancipated citizens of some means could fairly trivially possess their own private thermonuclear arsenal, an interplanetary shuttle powered by fusion rockets, or create their own space station with a carbon-allotrope hull. The only invariant technology projects which require any significant amount of cooperation or investment were massive megaprojects such as Dyson Swarms or radical biosphere alterations - and even then, the expense required hardly compared to the expense of more exotic infrastructure.
Arachne has an invariant matter printer - and as she has noted, it may well be completely irrelevant.