[quote][b]Posted by:[/b] Gourlay Quality After playing all the Halo's and paying close attention to the story line as best as I can I still don't really understand the Flood. How did they come to be, who and what exactly is the Gravemind, etc.[/quote] Precursors created them as a way to test humanity/get even with the Forerunners after they bought them down to near extinction in the Precursor-Forerunner war. The Gravemind is the composite mind created when the Flood infect sufficient beings and is the one responsible for controlling and directing their every move.