While the borg has been done to death, it might be EPesquely creepy to have someone who steals and incorporates *parts* of other people's egos into itself. Imagine an AGI that extracts useful skills from captured victims and uses them as skillsofts. Each skill will be tied to a particular personality or style: when speaking French the AGI speaks with a thick Quebecoise accent, when hacking it hums old J-pop, and when trying to negotiate it seems to be religious. You could have a group of these mindstealers: each a somewhat random agglomerate of parts and personalities, driven by a ruthless core mind. They are housed in equally cobbled-together synthmorphs or badly assembled cyborgs based on captured biomorphs (some of which are still conscious and individual, but had their motor functions rerouted due to crude puppeteer implants). Maybe the remnant of an old military or research installation from before the Fall, taken over by the not-quite-ready-for-primetime software and now quietly pirating through the asteroid belt for spare parts and more skills. It might not be an existential threat or super-smart, but it would be creepy as hell.