The big pink Forerunner elephant in the room.

Someone has to say something eventually(assuming something hadn't been said already). The Legendary Planet. What do you think it is? Onyx? A different shield world? Something new entirely?

I think it's probably something entirely new, it'd really give that sense of mystery and wonder the beginning of a second trilogy needs to start off with. Hopefully human-free since it's billions of miles away from any human settlements we know of.

Ohwait, I forgot my borrowed speculation from Bungie.net.

In Halo 2 or one of the novels that covers Halo 2, Cortana shows that AIs can make copies of themselves(which she did for some reason I don't care about anymore). Perhaps Mendicant Bias made copies of himself in every Forerunner installation he could, including the Legendary Planet(which I assume the thing in the trailer to be). He requests something of you and you refuse, for which he turns the installation and every Forerunner thing in it against you. You'd have to fight Sentinels and whatever else this thing has in it. With the Forerunner weapons since there'd be no other humans(and as such no other human weapons to cannibalize ammo from).

EDIT: And whoever's got the authority to do so, do you think it'd be a good idea to make the Halo 4 trailer the forum header?

Okay. Shane, Guugley, would the Halo 4 trailer make a good forum header?

And the Forerunners were the most advanced civilization ever(minus the Precursors but they probably went into another dimension or something). They've got to have SOME weapons worth using. Maybe the pistol has one of those kinetic things like those flashlights you shake to charge. Not sure how that would work for bullets, though...

Well everything else Chief has activated and deactivated so far(Halo ring, the Ark, a few terminals, sentinel beams, maybe some more stuff) has been fairly straightforward. And Forerunner tech seems to love humans for some reason.

I'll need to read Halo Cryptum sometime. It's supposed to be about the Forerunners iirc. Maybe it'll shed some light on it.

Oh, and keep in mind it's not just Chief's brainpower figuring out what the tech would do, he's also got Cortana with him.

I've only read Contact Harvest and read up on some of the lore on the Halo wiki. If I had enough money I'd go out and buy all the Halo novels, just because they're good books in their own right from what I've read.

I was wondering when this question would be asked. I don't doubt it for a minute. That planet/space station/shieldworld thing was indeed foruner. But like it has been suggested it is probably something new that hasn't been mentioned in the books or any of the previous games. Since the story of Halo 3 was effectively wrapped up and Halo 4 has been announced as a "new trilogy" it is plausible to assume that the writers are starting fresh and this forunner thing may be apart of it. All we can really do now is wait for more to be revealed. Only then will we be able to find out what this thing is.

It could be Onyx, but it would depend on exactly what the portal did to your ship at the end of Halo 3. When you're on the Ark, you're actually outside the galaxy. You can see the Milky Way in the sky. Onyx is well-within the galaxy. So if you simply floated away from the Ark into intergalactic space, then the world you're at couldn't be Onyx.

Whatever it is, it is almost certainly Forerunner. The architecture design is similar and has the same glyphs, and if you watch Halo: Legends, they show the same planet while Cortana begins discussing the history of the Forerunners.