The swap is dark, moist and stinky, and that's just the way its resident witch loves it. Metallia isn't bothered by being confined to the swamp's borders because really, why would she want to be anywhere else? Plus, if she turns everything to swamp then it's not like the limitation is going to be much of a problem. Not only does Metallia get to transform the world but she also has the pleasure of crushing and tormenting all the idiots in her path. There's simply no downside here.