Screenshot from The Sprint, showing the three known classes of Armiger. The central one is nearly identical to the Warden Eternal from the campaign demo, except it's holding a Light Rifle. The Warden Eternal will probably be sticking with that sword thing. And according to Halopedia, two of the three classes are Enforcers and Captains.

So, is the Warden an Armiger Captain, or a higher rank? Is the missing rank simply called a "Soldier"?

Another screenshot, concept art.
How does this work? Is there some sort of hardlight body under that armor? Is the Armiger some sort of android?

I'm reminded of early concept art of the Promethean Knight, where there was some sort of organic inside, piloting the armor.

This pose seems to be the Soldier's equivalent of the Knight splitting open its faceplate and screaming. In every other screenshot I've seen, the floaty bits aren't as prominent.

Wonder if there's a gameplay element to shooting them off?

Another screenshot of the Soldier.

Spoiler alert: I'm about 3/4ths of the way through Hunters in the Dark, and I'm far from impressed with these guy's combat records. They've ambushed the heroes in favorable terrain twice so far, and have inflicted zero casualties. That makes them less effective than two packs of feral animals. =\

There's an interesting backstory in the last Canon Fodder, which explains that the Armigers were designed to board and raid ancient Human ships. I don't think it's a very satisfying explanation, but some thought has gone into them.

During their war with ancient humanity millennia ago, the Didact employed the use of Armigers – bipedal combat platforms that proved incredibly useful for raiding ancient human warships, particularly when attempting to infiltrate the often-more confined spaces of human vessels.

Following the conflict, after the Didact had entered into exile during the ecumene Council’s diminishment of his rate, the Forerunners found themselves dangerously underprepared for the Flood’s return. In order to bolster the empire’s defenses, the Master Builder recommissioned the production of the Armigers to support the ranks of both Builder Security and the waning number of remaining Warrior-Servants. The Soldiers are one such example of these combat platforms, with multiple types used by various factions within the Forerunner ecumene.

While most were originally expended in the fruitless war against the Flood or compromised by the logic plague, some were secretly left to guard key Forerunner sites in the ages following the firing of the Array. Their reappearance with the Guardians indicates the secret of their manufacture has once again been uncovered, and as humanity continues to try and reclaim the vestiges of the Forerunners’ dominance, the reawakening of these constructs and others like them cannot be taken lightly by the UNSC.

The Warden Eternal, Keeper of the Domain. Note the hand with four fingers and two thumbs. It also seems interesting how bifurcated the hand and forearm look from the front. With a little work, he could signal "Live long and prosper" all the way up to his elbow!

Also take note of the Armiger behind him, which seems to be an identical model.

Bonus: Makes me think of Isaac Hannaford's work.

Thanks to Haloarchive's E3 Roundup