I'm creating my first world as a GM, and I had the idea of putting a city on the map in the middle of a desert, except when the players arrive there is nothing, only sand. The villain is going to be a necromancer, and I imagine that he casts "Cursed Earth" on the area to turn the residents into zombies, then possibly uses "Polymorph any Object" or some similar spell to turn the buildings into sand, thus leaving nothing but a bunch of zombies buried in the sand.
Couple questions: Does my choice of spells make sense, in case they detect magic and spell craft to see what happened? If not does anybody have a better idea of how a city turned into sand covered zombies?
Next question, does this idea seem like a fun plot point? Again, first time creating my own world to GM, I don't want to create a concept that won't be fun for the players.
Any suggestions are helpful, I'm pretty new to tabletops and would love some advice!
Thanks.