Someone probably already asked but it’s doesn’t look like it’s dark or in a desert
Black is the entity that follows you around and guides your missions. Desert is because and this is my point of view, but it’s for the lands you travel across some are desert scenes to swamps. Black swamp doesn’t sound good so I assume black desert was their go to.
Maybe the devs just liked pudding. Pudding is a "black[ish] dessert" 🤷🏼♂️