I think it would be super cool if we had more world altering spells, like the ones that remove mountains or terraform the land to add / remove various terrain features. One such spell that would be awesome to see would be something that summons a volcano! I could see it as a terrain feature that requires upkeep to stay active like the umbral portal spell, but when you stop paying the mana it could then just become a dormant valcano / mountain. Would be a nice way to add some more variance to the world when you start unlocking those big end game spells.