Ok may piss people off or not, and more to ponder. So I've stated osiris pretty much owns the vex...or basically helps them have a foot hold in the system. Reason he keeps creating the root mind. The simulation runs through all the time lines and figures out where best to place the vex in a mission. On the tree of probabilities (or possibilities can't remember the name) mission, while facing panoptes, the tree is behind it's head, each side that you run up and throw the arc charge down, gets rid of one side. Once panoptes is down, the tree is one line, and osiris is only left. Then he claims the forest is his (some more mission text), and he creates the root mind (which does the simulations fast enough to have built the spire, from what can be told, the same, and has its own sentience). To me this also means it must also have a present seed, and a future seed. Also, this why he needs to be killed. Why? He asks you to gather root minds corpse, cause "it may be valuable later". He is allowing the root mind to simulate what the vex are to do. Edit: I don't think he needs to die anymore, I think he is fundamental for the games reality.