Interested in more details about the campaign. Which ruleset? And what's the grid situation you have going on there where it turns to grass?
Mike D. is staying with the 2014 version of DnD 5E. Adamant about it, in fact.
I'm just a casual observer/player, and don't want to stick my hand in the dogfight that is DnD fandom.
The grid continues. There are stands of terrain on top of it, is all.
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Are you asking about the campaign setting? It's a homebrew that's been simmering in his brain for a decade +.