To all of this "Forerunner created Flood" discussion, I would simply re-ask the question: If you are going to wipe out, and then subsequently restore, every single sentient life form larger than a pig, in the
entire galaxy to kill the Flood, why in the name of all that is holy would you retain samples of it in your lab? If the Flood was simply a fire that had to be put out, and once extinguished would never return, then you wouldn't retain samples. Once destroyed, the galaxy would remain safe for eternity. Right?
From Episode 1:
KNOW THAT ENERGETIC AND TENACIOUS AS LIFE IS IT HAS AN ANTITHESIS JUST AS POWERFUL
This suggests that the Flood is something as fundamental as life, as natural as life. Nowhere in the Haloverse have I ever observed a single reference to the word "created" or anything like it associated with the Flood. Not in the books, not in the games, not in Iris, not in ILB, nowhere.
From Episode 2:
It has done this before elsewhere
Yes, I've heard the interpretation that this indicates it tried to contact them before, or whatever, but that's bunk. This suggests that the Flood is no remote phenomena, no singular occurrence. This, combined with the quote from Episode 1, might lead one to the belief that wherever life arises, the Flood eventually emerge as well. Wherever life emerges, death emerges to balance it. To counter it.
From Episode 3:
Who has the right to live? The light with the will to create me? Or dark with the will to consume? Sometimes might is right, and sometimes the lamb must submit to the lion
Consider this and the quotes above as well. The entity that is speaking in this final quote is attempting to resolve a philosophical issue; does something
good (light) have a more divine right to exist than something
bad (dark)? If the cold, merciless, machinery of the universe is natural selection; if the universe exists simply to create the most powerful natural biological mechanism, should this entity stand in its way? Should it allow the light to win(read:
avoid losing) the chess match by wiping the board clean?
All of this together points me towards the conclusion that the Flood (i.e.
death) is as naturally emergent as life, and just as powerful (if not more so). The Flood is natural. This provides for a more epic scale to the conflict that the standard Frankenstien morality tale, no?
Why did the Forerunner preserve Flood on their Halos? To give us a head start. To allow us to pursue a solution before the Flood appeared. Because they new, inevitibly, the Flood would return.