Across the Desert is a new Heroes of Might and Magic IV map by Vlad Ferariu. It's a small map with underground that requires the Winds of War expansion. You might remember seeing it in the maptesting section of this site some time ago.

"Embarking on a quest to save their kingdom from the desert curse, Gael and Clara find out there's more to it that they had expected..."

The good thing about this whole adventure thing is that there is always more to it than you expected!