What's wrong with Planes? Planes rock. More to explore. More to conquer. Efficient way to require enemies to team up to defeat a more powerful enemy, etc.
I dislike them from a cosmology/worldbuilding perspective, rather than from a gameplay perspective. In terms of gameplay, they're fine. We don't need them for the sake of more content, however, since the potential size of an Elemental map is unbounded.
I really like the spell. Does casting it in an enemy territory count as an act of war I wonder.
i think its a global enchantment so no need to cast it anywhere
I am pretty sure the idea is that it creates a tile on a targeted square, and enemies spawn from there. While you could get a different working with creative interpretation, that would merely detract from the thing.