Once the Empire was firmly established, the Forerunners began to expand once more, growing on an ever increasing scale beyond the old Consiliar frontiers - all for the greater glory of the Imperium! This period of expansion lasted at full speed almost three entire Cycles - The ninth to the eleventh, and sporadically continued into the twelfth, finally sputtering out completely only in the thirteenth Cycle. During this glorious period the "Pax Stellaris" of the Empire of the Night's Skies spread throughout a rough sphere - with its centre, as one would expect, on Home. At the height of Imperial magnificence, the round-trip journey time from Home to the outermost planet of the Imperial took a staggering THIRTY-FOUR years! Assuming that this figure refers to the use of the standard 10 LY per day Starships, within the parameters mentioned for the Consilium, this give us a radius of 4500-7500!

Within the borders of this unprecedented Interstellar state, a Citizen could travel freely, and free from danger, in any direction he choose - for purpose of Trade, Commerce or simply to see the sights! One common language - "The Tongue of Heroes" (perhaps more accurately rendered as "The Sacred Tongue" or "The Ancient Tongue") - was spoken everywhere, by the educated and those involved in trade, at least - giving the Empire a true "vox stellaris" to bind together the many disparate Forerunner races. The Imperium provided a single, uniform set of Civil , Commercial, and Criminal Law (the Mercantile League claim to recognise the concept of the "Sentient Commercial Being" in the law of the First Empire, but the evidence for this is highly dubious at best) to cover this vast sphere; it provided law and order in the spacelanes, encouraged Interstellar trade and generally created a seemingly perfect society that, Imperial Historians claimed - "will last until the Final Cycle of the Universe!".

This was not, however, to be the case. As the Empire expanded beyond the borders of the old Consilium, she came across Political entities consisting of races that had never been members. These independent States had mostly risen to prominence (i.e. had developed FTL technology) during or after the Consilium's collapse, or even during the Imperium's reconquista period. Many - most in fact - resisted the efforts of the Forerunners to incorporate them into their Empire. Of course, they were relatively quickly overwhelmed by the Imperial Military armed might.

As time went on, the number, size and organisation of such resisters increased - eventually to the point where the Imperium was increasingly hard pressed to continue her outward colonisating and civilising drive. Taxes were thus increased, and for a time ameliorated the problem - but eventually, the wave of Imperial expansion ebbed to the merest trickle, and gradually dried up altogether. Once this had occurred, the life of the Empire was limited, for much the same reasons as that of the cold Consilium hd been.

The major difference this time around is that the Imperium as such collapsed (considering its size) much more slowly than had the old Consilium. The conventional Forerunner explanation for this is twofold - the Imperial system had been so arranged as to eliminate all but the most minor differences between member planets (inadvertently, but nonetheless effectively), and also because the existence of strong extra-Imperial "barbarian" states existed to make obvious the need for a continuing Pax Stellaris within Imperial borders.

Despite this slowing effect, the pattern of collapse was inevitably started once expansion stopped - the Empire had simply become to big. Like an ancient Dinosaur, the beast could actually be dead and still move and fight because news of its death took so long to reach its brain. By the latter half of the ninth Cycle the collapse was becoming obvious, and, though the Emperors and their Starforces strove mightily to reverse it - a struggle with many seeming successes that were only temporary pauses in the downward spiral to chaos - the rate of collapse accelerated.

By the last Cbluvoe of the thirteenth Cycle, the collapse back in Barbarism had, again, brought down all but a handful of worlds. The major difference was that this time the Imperium had - whether through dint of luck or by implementation of long drafted plans - manage to salvage a nucleus based on a few score worlds in the vicinity of Home. Also, fortunately for the remaining Imperial worlds, the barbarian nations, bordering on the old Imperium had largely been destroyed, ravaged so badly that they too fell headlong into true Barbarism, or were sated with more conquered territories than they could assimilated. In any case, the Pax Stellaris was broken - and a veil of blackness falls over the once great Imperial sphere.