How do the halos work?
I don't mean the science, more what they achieve. Since I've heard they:
Kill everything, flood included
Kill everything but the flood, which then died of starvation after the fact with no living food.
If 2, how did the burn work, since they were areas completely consumed by the flood but where the flood was still active. So did external flood bring living food back or did the domain of it all transfer the necessary living food needs?
Additionally, if it did die of starvation how long does that take? Since the forerunners then did the reseeding effort and needed to purge all the dead stuff so it didn't kill the plant life. So there were bound to be planets were the flood was but hadn't fully consumed yet or were newly on.
Was the burn left alone or did they need to purify that of the dead flood mass?