"Choose among leaders possessing elite skills that can turn the tide of battle."
It may not have mentioned the covenant as playable, but it did have the above quote.
1. "elite skills", might the covenant not have elites?
2. are the "leaders" heroes or minifactions? (may not be currently answerable)
Edit: Where is the color change option for text? is it disabled for Safari?
A Halo Wars Story: Once upon a time, there was a light bridge. On that light bridge, there were many covenant. When the UNSC turned the bridge off, the covenant fell. The End.