This is another one of those shots that makes it hard to distinguish between in-engine footage and concept art.

Across the landscape we get a closer look at the objects on the floor. They're clearly not natural stalagmites, although it's also not clear that they are (or were) figures.

Some semi-transparent tendrils seem to stretch over the area, looking like spiderweb. This shot reminds me of The Tain from Myth.

In the background we can see some arches that look like Forerunner structures.