With all the references to Deserts in Champion's Odyssey, I'd like to clarify exactly what Desert Terrain is.
In the Seven Seas release there is a Terrain called Lost Desert. Lost Desert has the following text:
"Any Rivers and Lakes or Seven Seas bonus is reversed (ex. +2 Vitality in Rivers and Lakes is now -2 Vitality). No Vitality reduced below 0."
Any Desert Terrain referenced in Champion's Odyssey should be considered to have that same text, with one exception: no Vitality is reduced below 1.
Final note: Desert Terrain is not the same as Dry Heaps. They should be treated as 2 different Terrain types.