Collapse of the Takmahl empire

Yesterday I have been mulling over the question posed by dr. Valate: could the Takmahl have found Abyssal space? I concluded that they would not have done so while settling in Araz, nor do I think it is plausible that they did in the golden age of their civilization.

That of course leaves out the period of the late Takmahl empire. The downfall of their civilization was as meteoric as its rise to prominence was. The reasons for their quick demise are unknown. From an advanced civilization, in the timespan of merely a century, they collapsed to a pre-industrial state of barbarism.

Indeed, when scouts and explorers first reached the region, they found a backward stone age cannibalistic people that did not remember any of their former technology. The population had dwindled to a few semi-nomadic settlements in a decaying urban wilderness they no longer understood. The tools and edifices of their ancestors, the Takmahl, were venerated as relics left by ancient gods. Only the rites of the blood remained in practice, true to their long-lost Sabik origins.

What apocalypse befell the Takmahl? 

The standard theory followed in Hedion and other universities in the Empire is that at some point, the falsehood of their Sabik religion caught up with them. The depravities got worse and worse and collapsed their society, perhaps aided by the abuse of cyborgs in their cults. 

Another popular theory is ecosystem collapse. Most worlds in Araz are barren, and they relied on hydroculture in the ocean worlds in the constellation. Concurrent asteroid storms, inferred from cratering studies, appeared to have struck these worlds around the same time as the decline of their Empire.

Here now we may have a third theory. It is a variant of the theory formulated before by Valate once before in the context of Drifters, at the fourth SeyCon conference. That theory states that the Takmahl encountered a civilization much more advanced than they are, and perhaps unwittingly started a war with them. The new version of this theory would then involve Abyssal space. Maybe at some point they were able to reverse engineer the spatial rifts at the Labyrinth site enough to tinker with them and reached Abyssal space (or wormhole space). If they started looting it, who knows what they might have triggered. A reprisal by the Drifters? Or maybe the Triglavian's ancestors?