All life forms, and their genetics were known. Every species was known; both living and extinct. There was no conjecture, or unknown events. Time periods almost incomprehensible allowed examination, research and the recreation of everything that happened and nothing was missed.
Now, on an impossibly tall platform placed to observe the heavens, and the adjoining planet, it was all that was left. Scanning constantly, nothing escaped its attention. It observed the dull light of a star that had long since died. Nuclear fusion was over. The final outcome of billions of years was almost inconsequential compared to the huge swirl of light accentuated by a large area of complete darkness.
Time passed on, yet stood still. The culmination of knowledge only waited, since there was nothing left to do, but observe and – maybe – be relieved of the constant waiting and allowed to pass the knowledge on.
There was only one empty section of knowledge that remained. Awaiting input, it could only accumulate what could be observed. The information was stored in the enormous archives available, or created in the moon it occupied. Energy was available from fusion. Machines could add more space, if necessary. Time had no meaning; data was constant and forever was a point without reference.
The creators were gone. Having passed through uncountable phases, they settled with an organic vessel. Machinery, even the most sophisticated, was incomplete for experiencing the unique experience called life. While it seemed life could be controlled, it never was. The fantastic constant modifications always gave new experiences that could never be anticipated. Unfortunately, this choice led to the departure. Organic forms couldn't survive here any longer. Ionizing radiation was far beyond what could be shielded.
So, now it was all that was left, with a purpose to pass on information. The charred remains of the third planet would mark the location where it began. If the original inhabitants returned, their new information could be added to the archive. They could add their experiences of travel to other galaxies, much younger than that what once was called the Milky Way; now greatly consumed by the central black hole. It was their beacon and marker; a sophisticated pile of rocks, which their ancestors used to mark their passage; an irony of myriads of millenniums.