Well, you just got me to request a copy of Jonathan Strange & Mr. Norrell from my local library, so I'll tell you once I get a chance to read the book. Not being familiar with it, could I ask you to describe some of these fey?
In truth, the book doesn't have any stats for creatures. It's primarily a magic book, and the setting material is there to provide a framework to base one's own game upon. However, the setting is the creation of Jessica Jones (Acquana on the boards), and she has a lot of ideas to mine, so we're already considering working on a more detailed book that describes the setting. We just want to make sure that any book we put out has interest to anybody, not just people who are interested in the setting, though with luck, people who buy the book for the rules will end up intrigued by the world.
Fey from Gaia are not inherently cloaked, though true fey are actually fairly powerful and almost always have illusion powers. Other magical creatures that aren't true fey -- like sphinxes, elves, and ogres - might possess magic to hide themselves under an illusion.
One of the most common and easily purchased magical items are charms to make people who look at you think they're seeing something that makes more sense. They don't work on people who believe in magic, but they give players the chance to play something magical without getting too many funny looks.
Because the magic in this setting is heavily influenced by the beliefs of people, your game can even use classical creatures from fantasy and D&D, like Orcs and Illithids.
