Frogboy mentioned Populous
3D engines for doing very very nasty things to the game world when you have enough magic -- think Populous
To me it sounds like either one of the following:
1. Magic that uses essence create/destroy map terrain
OR 2. Map builder UI shows up allow gamer create/destroy map terrain tile & tile. Cost is paid by essence.
The question is how powerful you want? In good old Populous, you can sprout a volcano under your ememy’s city to destroy it.
What kind of effects you want?
It also sounds like some variation of material physics may exist for the game.
