I have based a lot of my own work on Thorn's Blackmoor on the timeline compiled by Simone Neri, found on Havard's Blackmoor site here.
There is very little canon material on Blackmoor just before the Great Rain of Fire, save that the society made vast amounts of progress in the thousand years since Uther declared independence from the Thonian Empire, and that this meteoric cultural rise is due to the technologies garnered from the City of the Gods, the Federation Survey Ship Beagle, which crashed into the Valley of the Ancients south of Blackmoor in UC 1019.
You can read about how Thorn's Blackmoor diverts from canon material on my blog, in the "Blackmoor, Thonia, and the Fey" series of articles, as well as the "Thorn's World That Was" series on Havard's blog.
Blackmoor in its last days is not really described in any detail, but hints are peppered here and there, and I have taken most of those and run with them to weave my own version.
In its Last Days, Blackmoor is in some ways a lot like Earth of today (they have ubiquitous information services, nearly-instantaneous communication); the Empire's spaceflight capabilities are about where they were on Earth in the 60s: orbit is in reach, and they've set their sights on the moon. Their environmental situation is a bit better off than ours, though. An energy similar to fusion has been teased apart from reverse-engineering the engines and power plants from the City of the Gods, and that power has been used as weapons in the wars against the Afridhi and beastmen. Combined with the energies and powers contained in the rare dragonstone minerals, it is little wonder that Blackmoor's enemies fear her weapons of war.
Blackmoor still has a king*, but is largely still ruled by the Regency Council, which consists of the elders from all the leading houses. This form of government simply scales up to the Empire level. Over the past century or so, some of the Guilds and Companies have been granted seats on the Regency Council.
*rumors abound that the line of kings after Uther were not the rightful rulers of the Kingdom after Uther passed away, but that his true heirs deserved the throne. Some say their refusal to assert their rights meant they were forfeit. Others whisper that the First King's daughters are simply biding their time, waiting for the opportune moment to take the Imperial throne and dissolve the Councils. Of course, as medical technologies have grown more and more advanced, the success rate of any such pretenders has become slimmer and slimmer as time goes on.
That opening pan of Asgard is pretty close to how I envision the Blackmoor metroplex, but there are portions of the city that are dark and dismal, as seen in Blade Runner.
The Regent's Council makes laws, or ratifies those proposed by the king, and the king pretty much takes care of enforcement. The king has much power, but it is curtailed by his having to cater to the Regent's Council.
The University, founded by Uther Andahar, was at one time an institution of the government, but soon grew beyond government, border and nation. It is very nearly a power unto itself, and if it ever decided to keep the fruits of its research for itself, it could very well make that claim and have the teeth to back it up. But all that research is costly, and the various governments within the Empire fund the various schools and branches within the University. It is very nearly the bundle of squabbling and politicking that the Empire's Regency Council is.