Silinrul achieved great degree of technological prowess, especially during their apex period. Transcendence was a great achievement, and so was the creation of Shoggoth Plague, despite how nonhumanitarian both were, but after the apex period their Empire entered period of slow decline during which most of said technologies were lost.
Silinrul warships are believed to use a modified strain of the Plague with heavy nanotechnological component that allowed them a great degree of self-repair without the need of crew to actually do something. Their computers were generally a few generations better than their current state-of-the-art cousins. After Transcendence the silinruls themselves could partially merge with the computer systems of their ships, causing a brief explosion of neural connection technology.
All of said achievements were already lost during last century of Silinrul history, due to their steady decline.
Rose to prominence together with the Silinrul Empire
around BC 8000 and soon conquered significant part of what is now known as Human Space. During their apex period (BC 6500-6000) their western border probably reached all the way into a current Plant Space, while the easter border of their remnants is close to the central sectors of the current Mantis Territory.
They enslaved or exterminated many species in an extremely cruel ways, all the way into selective breeding and gene/robomodifications to ensure docility and obedience. While their slaves were sufficiently pacified - with implants and genemodifications changing them into living zombies - the Silinruls lived in permanent fear of the Protectorates. The parts of space dedicated to hosting an umodified population of slaves species with breeding purposes. The modifications done to slaves was often bad for fertility, forcing the Empire to rely on marked breeding zones to supply it with enough slaves.
Their biggest trump card against the vast population of Protectorates that outnumbered the Higher Castes at least 10 to 1 was the Shoggoth Plague
, a geneengineered bioplague that could devour biomass of entire planets almost overnight. Every planet that dared to rebeled was scoured of all live without mercy, with the rebels unable to do anything to stop it due to the Silinruls having absolute monopol on starships.
Around BC 6000 they achieved the imperfect form of Transcendence, by moving the minds of entire Higher Castes into a robotic bodies. The Lower Castes soon disappeared in the masses of enslaved aliens, making the organic Silinruls go extinct before BC 5500. The machine ones remained around until the complete collapse of the Silinrul Empire
around BC 5100, due to losing control of Shoggoth Plague
expansion and massive slave rebellion known as Darkening