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
fairy
I'm a fairy that lives in the forest. I like to fly around with my siblings and play games. I try to hide from humans. If they find me, I'll grant their wishes.
I have programmed this to make you understand everything we wish to say to the world. Just be careful who you expose us to.  My cricket assistant will you carry it for me. Now, who exactly do you want to hear your message? You should start with the high priestess. She is gentle hearted but strong. I trust her. Wonderful idea. Do you wish to form an alliance? Yes. Give her this as a show of friendship. She will know it's significance. Do you have any terms for this alliance? No, no terms. You will know what to say when you study the crystal ball. Very well.  I am so glad we chose you to interpret us. You have always been diligent and through. It's my job and my pleasure. I love to help! I have always wondered, where do you go when you are not here with us? Do you have a family? My interpretations are my family. Binding people together with the power of translation is all the legacy I desire.