The major secret of the Circ Du Magic is of course that a huge number of impressive tricks really are magic and the circus itself harbours huge numbers of the supernatural, hiding in plain sight from the humans who watch them perform every day and night.
There are few rules in the circus for dealing with outsiders, but when looking inwards, there are a few. The circus is your family, so there is no stealing from inside, violence to circus folk is to be kept to a minimum. all secrets must be kept, and you have to work to earn your keep.