Can't wait to see how they look and how they work! :3
Getting really hyped over these fields. My speculations are: one is the Starry/Space/Cosmos field(probably for Anna and some legends), as previously speculated; a magnetic field for Titania; an air field of some sort for Heather(because I don't want her to battle on a mountain); a treasure field, dragon's lair/chamber, or something which weakens fairies for Saphira(probably the same as the area in which we might capture dragons and some pseudo-legends); and a greenhouse thingy for Bennet(cause forest field is distasteful for him imo).