As the dust blows away, the buried structure is revealed; an illuminated circumference punctuated by toothlike metal protuberances.

This shot's got everything; Banshees roaring by, frightened birds flying away, Covenant capital ships, a swirling vortex and lightning striking the surface of the artifact.

From the second sequence of distorted Cortana images, as she voices "I am your shield, I am your sword."

A clearly recognizable Cortana amongst the first sequence of distorted images.

In the distance, a figure walking towards the camera becomes visible.

The image of an arid African plain comes into view. Dust blows from left to right, and a public works sign with a picture of a grunt on it, very likely the "easter egg" referred to by Frankie in Bungie's FAQ, twists in the wind.

This Banshee roars over the head of the Master Chief in the Halo 3 Announcement Trailer, flying towards the mysterious buried artifact in the distance. But who is flying it? The cavity the pilot would normally appear in seems to be empty.

A delibrate omission by Bungie, to avoid revealing the species of Covenant currently invading? Or just a clever strategy to minimize the amount of artistic effort needed to create the trailer, thus ensuring the least impact on real development work?