They may have existed before the universe. The Gravemind tells us something impossible to understand— that most of what has been gathered comes from before there were stars. We do not believe in such a time, but the Mind insists … The life-patterns and living wisdom of a hundred billion years. Bear, Greg (2013-03-19). Halo: Silentium (Forerunner) (p. 322). Tom Doherty Associates. Kindle Edition. Their beings can reanimate as the Gravemind top the Didact he and the Primordial were the same. THE ONE THE Didact questioned on Charum Hakkor arrived on the margins of our galaxy nine million years before. That one was discovered by humans decades before the end of the war. We are the same. Bear, Greg (2013-03-19). Halo: Silentium (Forerunner) (p. 173). Tom Doherty Associates. Kindle Edition. You can only be Taken by having your will over whelmed, he can't take the Flood hive mind. Forerunner personal armor also have AIs which can reinstate a previous personality save if they detect a personality disorder. He also can only take so many people at a time. A few thousand I would guess.