[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.

I don't know, the Halo's defenses kicking in at minimum safe distance of 1 light year or any of the plethora of ships defending the Ring? The Precursors and the Flood are also trans-universal, so that the Vong live in another galaxy is moot. But you can't just say that the Vong would do something on the basis of "lol why not?" There are factors to consider as well, such as the Halo's being one of the most heavily defended installations in Forerunner space. What exactly can the Zombies do? And the Forerunners would eat the Mandalorian ground forces for breakfast. They would in fact win against any Star Wars ground force because Star Wars still has a modern military mindset. The Forerunners just tear apart the surface of a planet from the air, they only go into traditional ground engagements to root out specific targets. But to compare, Forerunner civilians wore armor 4 times as powerful as MJOLNIR by the end of the war, the Flood still breached them, because infection forms are only one way to get killed by them. Simply touching or breathing the same air will infect you without environment suits. Hell, once Keyminds are formed, simply being in the same star system can start causing feelings of unease/fear in the back of your mind.

[quote]Star Wars still has a modern military mindset[/quote] Have you seen the USNC forces? The zombies would do the same thing as the flood. They would basically just be exchanging infected members, leaving it at a stalemate.