[quote]What's to stop the Yuuzahn Vong (Who live in a different galaxy than the other factions) from terraforming the Halo array and taking control of it? [/quote] Good idea...but then you have to find these slipspace capable superweapons first. Let's not ignore the defense fleets guarding it that will make short work of organic vong fleets with hardlight weaponry, superior range, more numbers and better tech. A ring can lock it's surface into slipspace stasis making the surface impossible to reach or damage by the vong. The rings have defense weaponry with a range of 1 lightyear, vong fleets won't get near (it's possible this defense weapons can only attack ships in slipspace though). Even if the vong will somehow get through this, how in the end will these beings hope to control the very thing that they are against(vong hate tech) not to mention only Forerunners and reclaimers can use the Halo's. [quote]Or the zombies from the Star Wars universe to infect the Forerunners?[/quote] Which zombies? Whatever they are, they have to be at or above Flood level to have a chance against the Forerunners. I doubt they are. [quote]Heck, the Mandalorians have armor that light sabers cannot even penetrate, so how would the Flood or any other small-arms weapon penetrate it?[/quote] Hard light weaponry can disintegrate them. Even if mandalorian plates can take that damage, the rest of the body won't, as the warrior isn't entirely covered by this material. Telekinesis and physically powerful individuals like a flood juggernaut and a warrior servant will do the job too.