The dead Matrioshka brain filled the sky. A billion billion tiny fragments of smart matter
Transcendents never lasted long. Once the flesh was left behind, it was easy to fall prey to Dyson's folly. Civilisations digested planets, breaking them down and rebuilding them as shells of loosely coupled lumps of smart matter, spheres of processing power and memory, tuned to the optimum size to absorb solar energy and to radiate waste heat. Concentric shells would expand around a star.
Then came the wars. We could only imagine them, wars between aggregate intelligences and hive minds, between upload utopias and wild AIs. Like our oil and water wars, they were wars for resources. But now they fought for bandwidth and processing power, for control of smart matter and to control the flow of ideas. Trapped by the speed of light, by the speed of data packets, the inhabitants of the virtual worlds would be washed over by tides of conflict, buffeted by memes and viruses. Slowly individuality would be lost, and victorious intelligences would absorb new components.
There could be only one result. As minds became absorbed into a single intelligence, network latency turned the systems final mind against itself. In a paroxysm of senility, it would collapse into madness and death. An eternal scream as conciousness was lost in the darkness.
And then we came.
Our deepship came in slow. We were scavengers, looking for fragments of technology we could take back to Earth. Oh, we called ourselves archaeologists, and took great pleasure in the papers we published, but we were really grave robbers, stealing from the rotting corpses of the Singularity.