thanks for that Redshrike, good point on the confusion, it does seem like a contradiction. The idea is to imitate the dark ages in a galactic futuristic setting. there are a few points/differences to bear in mind.

1) The techs were restricted before the collapse of the empire due to problems involved with civil war and futuristic weapons (they were very devastating). One of the jobs of the empire (with the help of the church) was to restrict technology.

2) This is thousands of years in the future, Techs are very sophisticated, most can not be developed by normal intelligence but require huge artificial computers to develop. These computers are Lab or monasteries dedicated to a specific tech. Scientists are technically computer engineers. This has created a strange reliance on computers, so much so that techs that are obvious to us (e.g. simple battle tanks) still need labs to develop.

3) The Empire has collapses economically, structurally, hereditarily and as the universe was repressed politically, it has become reliant on the central power. The Empire was controlled through 4 offices: i) a spy/secret police network to counter insurrection ii) a naval force of space ships  iii) military force of legions and iv) a small Pretorian body guard. These offices still exist, although a shadow of there original force.

4) there is a concerted will by the church and the offices to resurrect the imperial power in face of the alien invasion, which is very serious. The guild (a group of merchants bent on monopolising what little trade is left) are also keep to see some kind of unity, although the centralised power of the empire is probably not to their liking.

5) to draw comparisons with a dark age Europe (all a bit mixed up): the Roman Empire has collapsed, Rome still exists, the church becomes an empirical linking force, the holy roman empire is formed, Spain and Constantinople are experiencing a powerful Mussulmen invasion, ancient knowledge from the greeks is being rediscovered, although the church is trying to control this knowledge. Europe begins to form through conflict and the development of nations after part or all of the empire, comparisons can be drawn to the Early Frank empire, the Byzantine Empire, or the later Holy Roman Empire

6) the capital world is (like the rome of old) a kindon unto itself, populous, industrial, rich, but dependent on trade. And has survived, this is the cornerstone of empire and from it it can be rebuilt.

7) rumor has it that some of the houses are behind the empire colapsing (the emporer was assainated), and the hole thing was preplaned, and  there in even a rumour (the church, bizarly, bans this thought as totaly heretical) that the aliens are not alien but a genetic experiment gone wrong.

8) given that many of the worlds are totaly dependent on others (moon worlds, colonies on exotic worlds etc aven agricultural worlds were dependent to a degree) for food, resourses, water, tech, machines, trade ect, the empire calapsing has had a very devastating efect in a short space of time (50 years, about), with complet world populations vanishing, or trying to survive by force, plunder, trade etc as best they can, many are reduced to basic food politics. This has cause a period on inward looking self centered colonies. Everybody has been conserned for themselves and basic survival, the idea of rebiuilding the empire seems ludicrous and imposible, but for a few, those few will be the houses the church, the guild, and the offices back. The house in a way are being manipulated, but wilingly. Some of these houses have may even have secret objectives not in the churches narrative.

II hope this makes sence. The idea in play, and how I hope these ideas translate, is to introduce a chaotic element: attacking other players while: using the offices to further ones own gain, diplomacy, church restrictions, aliens invading, revolts, awsome techs, starving peasants, civil war, subterfuge etc

There is another point, the church is not entirely religious, nor is its job just to restrict technology. The bishops, cardinals, and monks are basicaly what we would regard as historians and computer engineers. Each sect has a diferent view of the past. This is technicaly their doctrine. This may seem odd, but everything in this futuristic society is controled, including perceptions of the past, so while a devastating civil war was said to occur, another sect claims this war never hapened, one claims there was a second republic befor the empire, amother that no such republic ever existed. Perhaps the empire did not exist, that this is a new perception/creating to counter the alien threat etc. The church controls knowledge, and knowledge is the ultimate power. The houses are groups who are entirely dependent to their sect for their world view.