We kill that which we do not understand...and then promptly tea-bag it.
I thought the exact same thing. Especially when I read this part in Cryptum, "Somewhere in the humans' awakened memory lay our last hope of defeating the flood, which was even now ravaging world after world, system after system-more hideous by far than it had been a thousand years before. More sophisticated, more devious. More vital. And soon to acquire a new Master (the Prisoner possibly), if we did not act quickly-if we did not locate the lost installation and the former captive"(p.341-342). That can either be interpreted as the Flood is creating a new Gravemind, or it is near to its last living creator (the Prisoner). I will not rule out the possibility that after the Prisoner escaped, it may have fused with the Flood and served as its commanding intelligence, a foundation for the Graveminds to come. Otherwise, the Prisoner IS the last known Precursor.
[Edited on 07.25.2011 10:45 AM PDT]