No one has actually seen it, but a fairy interpreter asked a fairy and they described it as just a cloud of smoke and once in a while you trip over something in the floor.  The fairies purposely leave their trash in the floor because they think it is funny when people trip over them.
Inside the fairies church, Inside Church
fairy interpreter
bluebird
I am a bluebird that has made a nest in the castle walls. The king loves to listen to me sing every morning. My song fills the castle with music every day.
What a beautiful church! I will sing a song for it! Isn't it marvelous!  beautiful!  You voice is so majestic! I only wish there wasn't trash on the floor... Yes it is an eye sore, but when unsuspecting people walk through and trip over them, it so hilarious!  haha! if only they had wings like us! They are funny creatures! whoops! oh no! I just tripped over some garbage  Maybe if I would clear out all this smoke, you could have been that trash! so embarassing! My trash? Or the fact that you tripped over it?