Actually, halo would exist, even without the flood. The flood is on Halo because the forerunners and flood are against eachother and so are the humans and covenant. The flood are there because, of 1 infection form that is lucky to exist. In a dead room, infecting human and covenant bodies to turn them into combat form floods and putting some of them in a machine to turn anyone into carrier forms. Than the process repeats until the flod could take over the libary to get the index. Thats all in the first halo, but the second one, they do that also, but the humans and covenant are racing to get to it. The humans got to it first, but than Arbiter took them out, which took place in the level quartine zone after you compleate that level. So lets continue to what I was saying. Ok, so Johnson got knocked out by Arbiter, so than Keys daughter seen what was happening, than she was shooting Arbiter, but than he used his cloak so she couldnt see him and his shields could have been low. Than out of nowhere, three brutes came out, one chieften and 2 regular brutes took her out. The covenant got the Icon and than after that, the brute team has made their mind to whipe out all grunts, elites, hunters, and specially, Arbiter and the humans. But my point was halo can just be there without anyone or anything on it. The forerunners has created halo for some reason, but I dont know. I hope you read all this.